Grade 8 / Space, pyramid and cone 69 exercises (including 66 corrected)

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largeur(Longueur(LRectangleAL×petitebase(bgrandeBase(Bhauteur(hTrapèzeABb×h2côté(cCarrédAc2ABCTrianglerectangleAAB×AC2base(bhauteur(hTriangleAb×h2rayon(rDiamètre(DCercleP2×ı×rAı×r2 ABCDEF13m12m5m6mGHIJKLMN7cm4cm3cm3cm hauteur(hPrismedroitVAB×h ChingQuizz : 2 exercises available for Quizz assessment : 1. Straight prisms and cylinders: reminders E.9112 1 Consider the right prism P whose base is a nonagon. How many faces does the right prism P have? 2 The right prism Q has 15 edges. What is the nature of its base? Definition: names of polygons: Number of sides Name of the polygon 3 triangle 4 quadrilateral 5 pentagon 6 hexagon Number of sides Name of the polygon 7 heptagon 8 octagon 9 nonagon 10 decagon E.9058 Reminder : Below are the formulas for calculating the ar-eas of the following polygons: Consider the two right prisms shown below in cavalier per-spective : 1 Give the nature of the base of each of these right prisms and determine the area of their respective bases. Reminder : Opposite is the formula for the volume of a right prism, where A B represents the area of its base and h repre-sents the measurement of its height. 2 Determine the volume of each of these right prisms. https://chingmath.fr chapExoCorrec/9112 sacados/9112 chapExoCorrec/9058 sacados/9058 largeur(Longueur(LRectangleAL×petitebase(bgrandeBase(Bhauteur(hTrapèzeABb×h2côté(cCarrédAc2ABCTrianglerectangleAAB×AC2base(bhauteur(hTriangleAb×h2rayon(rDiamètre(DCercleP2×ı×rAı×r2 ABCDEF13m12m5m6mGHIJKLMN7cm4cm3cm3cm hauteur(hPrismedroitVAB×h
(d hauteur(hrayon(rCylindreSlatérale2×ı×r×hVı×r2×h 15cm3cm 3cm4cm5cm8cm 12cm15cm20cmABCDEF E.6449 In the table below, for each row, re-trieve the volume value on the left and convert it using the unit shown on the right : km 3 hm 3 dam 3 m 3 dm 3 cm 3 mm 3 312 m 3 . . . dm 3 0 ; 32 dm 3 . . . m 3 350 mm 3 . . . m 3 2 . . . m 3 33 c‘ . . . cm 3 25 km 3 . . . m 3 Recall the equality : 1 =1 dm 3 E.9059 1 a A right prism has a triangular base. How many faces does this solid have? b A right prism has a hexagonal base. How many edges does it have? 2 a A right prism has 12 edges. What is the nature of its base? b A right prism has 7 faces. What is the nature of its base? E.9064 A tiered cake consists of 3 cylindri-cal cakes stacked on top of each other, all centered on the axis ( d ) , as shown in the figure below : The three tiers of the cake are all 8 cm high, and the respective diameters of these cylinders are 30 cm , 20 cm , and 10 cm . Determine the volume of this cake. Round the volume to the nearest cubic centimeter. Reminder : The lateral surface area and volume of a cylinder are given opposite, as a function of the radius of its base and its height. Hint: we will use : ı 3 ; 1416 we will round the intermediate results to the nearest cubic millimeter. E.9110 Below is the pattern for a cylinder: Determine the height of the cylinder and the radius of its base. If necessary, round the values to the nearest millimeter. Note: we will use : ı 3 ; 1416 E.9659 We consider the right prism below : Determine the volume of this solid. E.9660 Consider the right prism below whose base is a right triangle in A : Determine the volume of this solid. 2. Prisms and cylinders: enlargements and reductions https://chingmath.fr chapExoCorrec/6449 sacados/6449 chapExoCorrec/9059 sacados/9059 chapExoCorrec/9064 sacados/9064 (d hauteur(hrayon(rCylindreSlatérale2×ı×r×hVı×r2×h chapExoCorrec/9110 sacados/9110 15cm3cm sacados/9659 3cm4cm5cm8cm sacados/9660 12cm15cm20cmABCDEF
10cm4cm2cmABCDEFGHMNPQRST ABCDEFGHABEF BAA E.9124 Definition: Let k be a strictly positive number. For k< 1 and when all dimensions of a plane figure or solid are multiplied by k , we say that we have performed a reduction by a factor of k . For k> 1 and when all the dimensions of a plane figure or a solid are multiplied by k , we say that we have performed an enlargement by a coefficient of k . Consider the right-angled parallelepiped ABCDEFGH shown below, with dimensions : AB = 10 cm ; BC = 4 cm ; CG = 2 cm We construct the right-angled block MNPDQRST obtained from the right-angled block ABCDEFGH by reducing its dimensions by a factor of 1 2 . 1 Noting A as the area of face ABFE and A as the area of face MNRQ , determine the value of the quotient : A A 2 Let V be the volume of the rectangular prism ABCDEFGH and V be the volume of the rectangu-lar prism MNPDQRST . Determine the value of the quotient : V V E.980 Proposition: If all dimensions of a plane figure is reduced or enlarged by a coefficient k then its area has been multiplied by k 2 . If all dimensions of a solid is reduced or enlarged by a coefficient k then its volume has been multiplied by k 3 . Copy the table belowbelow on your sheet of paper and com-plete it using the square root keys x et racines n ième x y k k 2 k 3 5 16 729 E.9118 The Aztec calendar preserved in Mexico City’s National Museum of Antropology has a diameter of 3.60 meters and weighs 25 tons. What would be the weight of a replica 20 centimetres in diameter? (round to the nearest decigram) E.9115 In this pan, you can prepare a paella for three people. Taking a pan four times the size, how many people can we invite? E.9116 The radius of the large cylinder has been halved. By how much has its vol-ume been reduced? E.9119 In the figure oppo-site, the parallelepiped A B C DE F G H was ob-tained from ABCDEFGH by reducing its length and width by 2. By how much has the vol-ume of the parallelepid de A B C DE F G H been re-duced. E.4210 The volume of the parallelepiped has been multiplied by 27. By how much have its dimensions been en-larged? E.9122 The volume of the small paral-lelepiped is 14 dm 3 . The ratio BA BA of the heights of the two parallelepipeds is 1 = 3 . Calculate the volume of the large par-allelepiped. 3. Right prisms and Pythagorean theorem https://chingmath.fr chapExoCorrec/9124 sacados/9124 10cm4cm2cmABCDEFGHMNPQRST chapExoCorrec/980 sacados/980 chapExoCorrec/9118 sacados/9118 chapExoCorrec/9115 sacados/9115 chapExoCorrec/9116 sacados/9116 chapExoCorrec/9119 sacados/9119 ABCDEFGHABEF chapExoCorrec/4210 sacados/4210 chapExoCorrec/9122 sacados/9122 BAA
ABCDEF Baievitrée8m4;2m0;5m0;79m ABCD0;79m4;2m0;5m arrièredroiteface avantgauche ABCDEF ABCDEFGH7cm24cm15cm10cm E.6450 Consider the right prism ABCDEF shown below : The following measurements are given : AB = 6.5 cm ; AC = 1.6 cm ; BC = 6.3 cm ; AD = 3 cm 1 Show that the triangle ABC is a right triangle. 2 Determine the volume of the right prism ABCDEF . E.9068 Mrs Martin would like to create a concrete terrace in front of her bay window. She produces the drawing below, indicating the measure-ments. To facilitate rainwater run-off, the terrace floor must be sloped. The terrace is shaped like a right prism with a right-angled trapezoid at its base. 1 Determine the volume of concrete required for the terrace design. 2 Below is a profile view of the terrace. a Determine the length of the segement [ CD ] . b Deduce the surface area of the terrace. E.6452 We stacked and glued 6 cubes with edges of length 4 cm and a right prism to obtain the solid shown below. The height of the prism is equal to half the edge length of the cubes. 1 Draw a full-scale view of the rear of the solid. 2 Calculate the volume in cm 3 of the solid. 3 Study of the right prism. a This prism is called ABCDEF , as shown in the figure below : What is the nature of the base of this right prism? Justify your answer. b Verify by calculation that the length is AC = 32 cm . c Deduce the exact value of the area of face ACFD . Round to the nearest mm 2 . E.9065 Consider the right prism ABCDEDFGH whose base ABCD is any quadrilateral, but has two right angles at vertices B and D . 1 Determine the area of the base of this right prism. 2 Give the volume of this right prism. https://chingmath.fr chapExoCorrec/6450 sacados/6450 ABCDEF chapExoCorrec/9068 sacados/9068 Baievitrée8m4;2m0;5m0;79m ABCD0;79m4;2m0;5m chapExoCorrec/6452 sacados/6452 arrièredroiteface avantgauche ABCDEF chapExoCorrec/9065 sacados/9065 ABCDEFGH7cm24cm15cm10cm
Pyramide ABCDSTEFGHIJ ABCDEFS GHIJKLS ABCDEFGHIJKO 4. Pyramids: properties E.4958 Definition: The pyramid is a solid with a polygonal base and a point called vertex (also called apex) which is connected to all the ver-tices of the base. Proposition: If the base of a pyramid has n vertices, the pyramid contains 2 n edges and n +1 faces. Consider the two pyramids below : 1 Consider the pyramid ABCDS : a What is the nature of the base of this pyramid? b How many edges does this pyramid have? c How many faces does this pyramid have? 2 Consider the pyramid EFGHIJT : a What is the nature of the base of this pyramid? b How many edges does this pyramid have? c How many faces does this pyramid have? E.9111 1 Consider the pyramid P whose base is a heptagon. How many faces does the pyramid P have? 2 The pyramid Q has 18 edges. What is the nature of its base? Definition: names of polygons: Number of sides Name of the polygon 3 triangle 4 quadrilateral 5 pentagon 6 hexagon Number of sides Name of the polygon 7 heptagon 8 octagon 9 nonagon 10 decagon E.4952 Consider the two pyramids ABCDEFD and GHIJKLS with hexagonal bases shown below. The first pyramid is random while the second is a regular pyramid. 1 Can the foot O of the height of the pyramid ABCDEFS from S be traced precisely. 2 Place the point O representing the foot of the pyramid height GHIJKLS originating from the vertex S . Jus-tify your approach. Definition : A pyramid is said to be regular if its base is a regular polygon (equilateral triangle, square, regular hep-tagon. . . ) and if the foot of the height is the center of its base. E.4954 Consider the right-hand paving stone ABCDEFGH shown below : K is the middle of the segment [ EH ] ; I is the center of the face ABCD ; J is the center of the face EFGH ; O is the center of the cuboid. Give the natures of the solids below and state their base and height : a ADCEHG b ADCE c DICO d EKGF 5. Pyramids: volume https://chingmath.fr chapExoCorrec/4958 sacados/4958 Pyramide ABCDSTEFGHIJ chapExoCorrec/9111 sacados/9111 chapExoCorrec/4952 sacados/4952 ABCDEFS GHIJKLS chapExoCorrec/4954 sacados/4954 ABCDEFGHIJKO
Pyramide ABCDEFGHOS12m8m4m3m ABCDHS230m146m ABCS15cm25cm21cm ABCDHS24m18m25m E.4902 Proposition: Let P be a pyramid of height h and whose base has area A . The volume V of the pyramid has measure : V = 1 3 ×A× h A house is built by superimposing a right block ABCDEFGH and a pyramid EFGHS with vertex S . The representation below specifies some measurements : Determine the total volume of this house. E.9066 The pyramid of Cheops, located in Egypt, is a square-based pyramid whose base sides measure 230 m and the height, at its construction, measured 146 m . Here is a representation of this pyramid: 1 Determine the volume of the pyramid of Cheops, rounded to the nearest cubic meter. 2 Assuming that all the stones in the pyramid are iden-tical and that each has a volume of 0.95 m 3 and that each weighs 2.1 tons. Determine, in kilograms, the total weight of the pyramid of Cheops. 6. Pyramid and Pythagorean theorem E.9130 In space, consider the pyramid ABCS whose base ABC is a right triangle and whose ver-tex is point S . Also, the ABS face is a right triangle in A and the CAS face is a right triangle in A . The following dimensions are given : AB = 15 cm ; AC = 21 cm ; BS = 25 cm 1 Establish that : AS =20 cm 2 Determine the volume of the pyramid. E.5675 Consider the pyramid ABCDS shown below o where the base ABCD is a rectangle and H is the foot of the height from the vertex S and the middle of the segment [ AC ] : 1 Show that the segment [ AH ] has length 15 m . 2 a Determine the length of the height [ SH ] . b Determine the volume of the pyramid SABCD . https://chingmath.fr chapExoCorrec/4902 sacados/4902 Pyramide ABCDEFGHOS12m8m4m3m chapExoCorrec/9066 sacados/9066 ABCDHS230m146m chapExoCorrec/9130 sacados/9130 ABCS15cm25cm21cm chapExoCorrec/5675 sacados/5675 ABCDHS24m18m25m
ABCS24cm37;3cm34;8cm ABCDEFHGMN EHGFADCBIJK ABCD E.9131 In space, consider the pyramid ABCS whose base ABC is a right triangle and whose ver-tex is point S . Also, the ABS face is a right triangle in A and the CAS face is a right triangle in A . The following dimensions are given : AB = 24 cm ; BC = 34.8 cm ; CS = 37.3 cm Determine the volume of the pyramid. E.981 ABCDEFGH is a right-angled parallelepiped. M is a point on the segment [ FG ] and N be-longs to the segment [ EF ] The following measurements are given : FE = 12 cm ; FG = 9 cm ; FB = 3 cm FN = 4 cm ; FM = 3 cm Here is a representation of this configuration : 1 Calculate length MN 2 Show that the area of the triangle FNM is equal to 6 cm 2 . 3 Calculate the volume of the pyramid ( P ) with vertex B and base the triangle FNM . 4 Consider the solid ABCDENMGH obtained by remov-ing the pyramid ( P ) from the right-angled parallelepiped. a How many faces does this solid have? b Calculate its volume E.3275 Reminder : volume V of a pyramid: V = (aire de la base) × hauteur 3 ABCDEFGH is a cube with edge length AB =12 cm . I is the midpoint of segment [ AB ] ; J is the midpoint of segment [ AE ] ; K is the midpoint of segment [ AD ] . 1 Calculate the area of triangle AIK . 2 Calculate the volume of pyramid AIKJ with base AKI . 3 What fraction of the volume of the cube does the vol-ume of pyramid AIKJ represent? Write the result as a fraction with numerator 1 . 4 Draw a template of pyramid AIKJ . E.4951 Consider the pyramid ABCD with a triangular base : AB = BC = BD ; AC = AD = CD = 5 cm In addition, the ABD , ABC , and BCD faces are right-angled triangles at B . 1 In the triangle ABC , determine the measure of segment [ AB ] rounded to the nearest millimeter. 2 Determine the volume of the pyramid ABCD rounded to the nearest cm 3 . 7. Pyramids and Thales’ theorem https://chingmath.fr chapExoCorrec/9131 sacados/9131 ABCS24cm37;3cm34;8cm chapExoCorrec/981 sacados/981 Groupe Sud - Juin 2003 - 7 points ABCDEFHGMN chapExoCorrec/3275 sacados/3275 Brevet juin 2010 - 6 points EHGFADCBIJK chapExoCorrec/4951 sacados/4951 ABCD
ABCDMNPQHSH ABCDEFSH ABCDMNPQHSH ABCDHSMNPQHS E.9125 Consider the pyramid ABCDS whose base ABCD is a square such that : AB =9 cm ; SH =12.75 cm ; SB =14.25 cm We construct the pyramid MNPQS whose base MNPQ is a square parallel to the square ABCD and such that : SN =9.5 cm Determine the measure of height [ SH ] of the pyramid MNPQS . E.9106 We want to build a teepee in the shape of a pyramid with a rect-angular base ABCD centered at H and height [ SH ] (see the diagram opposite) . The teepee will have the follow-ing dimensions : AD =1 ; 60 m ; CD =1 ; 20 m SH =2 ; 40 m ; SF =1 ; 95 m SD =2 ; 60 m 1 Calculate the volume V of this pyramid in m 3 . Reminders: V = 1 3 × B × h is the area of the pyramid, where h is the height and B is the area of the base. The frame of the teepee, consisting of the rectangular frame ABCD and the four side edges extending from S , is made of bamboo sticks. A rod [ EF ] is added to the frame as shown in the drawing so that ( EF ) == ( AD ) and SF =1 ; 95 m . 2 Calculate EF . E.9127 Consider the pyramid ABCDS whose base ABCD is a square such that : AB =9 cm ; SH =12.75 cm ; SB =14.25 cm We construct the pyramid MNPQS whose base MNPQ is a square parallel to the square ABCD and such that : SH = 8.5 cm 1 Determine the volume V of the pyramid ABCD . 2 a Establish that : SN = 9.5 cm b Establish that : MN = 6 cm c Determine the volume V of the pyramid MNPQS . 3 Establish the following equalities: SN SB = MN AB = 2 3 ; V V = 2 3 3 Hint: the calculator can be used to reduce fractions. E.9128 Consider the pyramid ABCDS whose base ABCD is a rectangle and whose vertex is S . The following dimensions are given : AB = 24 m ; BC = 18 m ; SB = 39 m 1 a Show that the segment [ BH ] measures 15 m . b Deduce that : SH = 36 m c Give the volume of the pyramid ABCDS . The point N belongs to the segment [ SB ] such that : SN = 26 m We create a section of the pyramid from the point N by a plane parallel to the base of the pyramid. We denote H the point of intersection of the cutting plane with the segment [ SH ] . The solid MNPQS is a pyramid with a rectangular base MNPQ and a vertex S , and the point H is the foot of the height from S . 2 Establish that : MN = 16 m ; SH = 24 m 3 Determine the measure of segment [ SH ] . 4 It is assumed that NP = 12 m . Deduce the volume, to the nearest cubic meter, of the pyramid MNPQS . https://chingmath.fr chapExoCorrec/9125 sacados/9125 ABCDMNPQHSH chapExoCorrec/9106 sacados/9106 ABCDEFSH chapExoCorrec/9127 sacados/9127 ABCDMNPQHSH chapExoCorrec/9128 sacados/9128 ABCDHSMNPQHS
ABCDHSMNPQHS ABCDMNPQHSH OABCDEIJKL HH HH 8. Pyramids: enlargements and reductions E.9104 Consider the pyramid ABCDS whose base ABCD is a rectangle and whose vertex is S . The following dimensions are given : AB = 8 m ; BC = 6 m ; SH = 12 m ; SH = 9 m 1 Determine the volume of the pyramid ABCDS . 2 a Justify that the reduction to obtain the pyramid MNPQS has a reduction coefficient of 3 4 . b Deduce the volume of the pyramid MNPQS . E.9109 Definition: A pyramid is said to be regular if its base is a regular polygon (equilateral triangle, square, regular pen-tagon. . . ) and if the foot of the height from the apex of the pyramid is the center of its base. We consider the pyramid ABCDS to be regular, whose base ABCD is a square and the foot of the height from S is the point H . We have the measurements : AB =9 cm ; SH =12.75 cm ; SB =14.25 cm We construct the pyramid MNPQS whose base MNPQ is a square parallel to the square ABCD . We denote H as the foot of the height of this pyramid from the vertex S . We have the measurement : SH =8.5 cm 1 Determine the volume V of the pyramid ABCDS . 2 Determine the length of segment [ SN ] . Hint: we assume that lines ( HB ) and ( H N ) are parallel. 3 a Determine the reduction coefficient applied to the dimensions of the pyramid ABCDS to obtain the pyra-mid MNPQS . b Determine the volume V of the pyramid MNPQS . E.4953 Consider the ABCDE pyramid with a rectangular base shown below and such that [ OE ] is the height of the pyramid and where O is the center of the base : The points I , J , K , and L represent the respective middles of the segments [ EA ] , [ EB ] , [ EC ] , and [ ED ] . We assume that : The solid IJKLE is a pyramid with rectangular base IJKL and vertex S ; bases ABCD and IJKL are parallel and we also have the relations : ( IJ ) == ( AB ) ; ( JK ) == ( BC ) AB = 16 cm ; BC = 12 cm ; EB = 26 cm 1 a Justify that the segment [ KJ ] measures 6 cm b We amdet that the base IJKL of area A is a reduc-tion of the base ABCD of area A . Give the reduction coefficient of the area A to obtain the area A 2 It is assumed that OE =24 cm . Determine the volumes V of the pyramid ABCDE and V of the pyramid IJKLE . E.9120 The volume of the Great Pyramid is 576 km 3 . The volume of the small pyramid is 9 km 3 . Establish equality: SH SH = 1 4 E.984 The height of the Great Pyramid measures 32 cm . The height of the small pyramid measures 8 cm . The volume of the small pyramid is 13 cm 3 . Calculate the volume of the large pyra-mid. https://chingmath.fr chapExoCorrec/9104 sacados/9104 ABCDHSMNPQHS chapExoCorrec/9109 sacados/9109 ABCDMNPQHSH chapExoCorrec/4953 sacados/4953 OABCDEIJKL chapExoCorrec/9120 sacados/9120 HH chapExoCorrec/984 sacados/984 HH
ABCDEFGHS ABCDEFGHIOI SABCDABCD E.982 The house model shown below consists of : of a right block of dimensions : AB = 30 cm ; AE = 20 cm ; AD = 5 cm topped by a pyramid of height 6 cm . 1 Calculate the volume V 1 of this model. 2 Knowing that this model is a coefficient reduction 1 = 50 of the real house, deduce from the first question the volume V 2 in m 3 of the house. E.986 The dimension reduction coeffi-cient is 1 2 . Knowing that the area of the base of the large pyramid is 24 m 2 , cal-culate the area of the base of the small pyramid. Knowing that the volume of the small pyramid is 56 m 3 , calculate the volume of the large pyramid. E.9117 The SA B C D pyramid was ob-tained by sectioning the SABCD pyramid using a plane parallel to the latter’s base. Knowing that the volume has been reduced by 64, determine the coef-ficient of reduction of the area of their common bases. 9. Pyramids: patterns E.4959 Cut out the pattern below of a tri-angular based pyramid and reconstruct the solid. E.4960 Cut out the pattern below of a tri-angular based pyramid and reconstruct the solid. https://chingmath.fr chapExoCorrec/982 sacados/982 Brevet - 3 points ABCDEFGHS chapExoCorrec/986 sacados/986 ABCDEFGHIOI chapExoCorrec/9117 sacados/9117 SABCDABCD chapExoCorrec/4959 sacados/4959 chapExoCorrec/4960 sacados/4960
ABCDEFGHIJK Schéma1Schéma2Schéma3Schéma4 ABCDEFGH rCônehauteur(h E.7979 The pyramid FIJK is cut out of the cube ABCDEFGH as shown in the adjacent drawing. The segment [ AB ] measures 6 cm . The points I , J and K are the respective middles of the edges [ FE ] , [ FB ] and [ FG ] . 1 Draw the triangle IFK full size. 2 One of the four diagrams below corresponds to the pyra-mid pattern FIJK . Indicate its number on the copy. No justification is ex-pected. E.6454 Consider a ABCDEFGH cube of edge 5 cm inside which the ABCDH pyramid has been carved. 1 a Determine the measurement to the nearest millime-ter of segment [ AH ] . b Determine the measurement to the nearest millimeter of segment [ BH ] . 2 a Give the nature and dimensions of each of its faces. b Make a pattern of the pyramid ABCDH . 10. Cones: volumes E.9067 Proposition: A cone with radius r and height h has a volume of : V = 1 3 × ı × r 2 × h Indication : we will use : ı 3 ; 1416 https://chingmath.fr chapExoCorrec/7979 sacados/7979 ABCDEFGHIJK Schéma1Schéma2Schéma3Schéma4 chapExoCorrec/6454 sacados/6454 ABCDEFGH chapExoCorrec/9067 sacados/9067 rCônehauteur(h
AOBOAcm2cm AOSS 3cm7;8cm3cm7;8cm SAHAHCC ASOI Consider a cone of revolution with height 5 cm and base radius 2 cm . Point A is the apex of the cone and O is the center of its base. B is the midpoint of [ AO ] . Calculate the volume of the cone at cm 3 . Round to the nearest whole number. E.5457 A marine signal buoy consists of two cones with the same base, as shown in the figure op-posite. The following dimensions are given : SO =0.8 m ; S O =0.5 m ; OA =0.25 m Determine the total volume of this buoy rounded to the nearest dm 3 . Note: we will use : ı 3.1416 11. Cones: properties, Pythagorean theorem and Thales theorem E.9108 Below is a cone and its template : The base disc has a radius of 3 cm and any segment of the lateral surface connecting the apex of the cone to a point on the base measures 7.8 cm . Determine the volume of this cone rounded to the nearest cubic millimeter. Hint: we will use : ı 3.1416 E.9126 Consider the cone with base C , cen-ter H and radius [ HA ] , and apex S such that : HA =6 cm ; HS =15 cm The cone is intersected by a plane parallel to its base and pasasnt through the point H of segment [ SH ] and such that : SH =5 cm . We admit that : the section is a circle C of center H and radius [ H A ] where the point A is on the segment [ SA ] . the straight lines ( A H ) and ( AH ) are parallel. Determine the measure of the radius of the circle C . E.983 Consider the cone shown oppo-site with vertex S and whose base is the disk of radius [ OA ] . This cone has height SO =8 cm and generatrix SA =10 cm . I is a point on segment [ SO ] such that SI =2 cm . Indication : we will use : ı 3.1416 1 Show that : OA =6 cm . 2 Show that the exact value of the volume V of the cone is equal to 96 ı cm 3 . Give the value rounded to the nearest mm 3 . 3 Determine, to the nearest degree, the measure of the an-gle widehatASO . 4 Cut this cone with a plane parallel to its base and pass-ing through point I . The resulting section is a disk with center I , a reduction of the base disk. a Determine the ratio k of this reduction. b Let V be the volume of the cone with vertex S and base the disk with center I . Express V in terms of V , then give the rounded value of V to the nearest mm 3 . https://chingmath.fr AOBOAcm2cm chapExoCorrec/5457 sacados/5457 AOSS chapExoCorrec/9108 sacados/9108 3cm7;8cm3cm7;8cm chapExoCorrec/9126 sacados/9126 SAHAHCC chapExoCorrec/983 sacados/983 Brevet - 5,5 points ASOI
SOBBONiveaumaximumde l’eau OAHAHCC OOAAS grC1C2¸ 4;2cm7cm4;2cm7cm 12. Cones: enlargements and reductions E.4204 In practical chemistry work, students use containers, called Erlenmeyer flasks, like the one shown below : The container is filled with water up to the maximum level indicated on the diagram by an arrow. Note: C 1 le large cone with vertex S et base the disk with center O et radius OB ; C 2 the small cone of vertex S and base the disk of center O et of radius O B . We give : SO =12 cm ; OB =4 cm Indication : we will use : ı 3.142 1 The volume V d of a cone of revolution of radius R et of height h est given by the formula : V = 1 3 × ı × R 2 × h Calculate the exact value of the cone’s volume C 1 . 2 The cone C 2 is a reduction of the cone C 1 . Given that SO =3 cm . a What is the coefficient of this reduction? b Prove that the exact value of the volume of the cone C 2 is equal to ı cm 3 . 3 a Deduce that the exact value of the volume of water contained in the container, in cm 3 , is 63 ı . b Give the volume of water, rounded to the nearest cm 3 . 4 Is this volume of water greater than 0.2 liters? Explain why. E.9114 The area of the base of the small cone of revolution is 5 mm 2 while that of the base of the large cone is 80 mm 2 . Calculate the area enlargement coeffi-cient. Deduce the coefficient of magnification of the dimensions. Knowing that the volume of the large cone is 384 mm 2 , determine the volume of the small cone. E.9121 The area of the small base is 27 m 2 . The area of the large base 108 m 2 . The height of the large cone of revolution is 1 m . Calculate the height of the small cone of revolution. 13. Cones: patterns E.9107 Below is the pattern of a cone of revolution : Express the measure of the angle ¸ , in degrees, in terms of the values of r and h . E.11081 Below is a picture of a cone and its pat-tern : The base disk has radius 3 cm and any segment of the side face, connecting the apex of the cone to a point on the base, has measure 7.8 cm . Hint: we’ll use ı 3 ; 1416 1 Determine the circumference of the base disk. https://chingmath.fr chapExoCorrec/4204 sacados/4204 Pondichery Avril 2010 SOBBONiveaumaximumde l’eau chapExoCorrec/9114 sacados/9114 OAHAHCC chapExoCorrec/9121 sacados/9121 OOAAS chapExoCorrec/9107 sacados/9107 grC1C2¸ sacados/11081 4;2cm7cm4;2cm7cm
(dno1no2no3 2 Deduce the angle of the pattern disk section. 3 Determine the area of the lateral surface of this cone. 14. Complex problems and tasks E.7961 Heiata and Hiro chose as their wedding cake a pièce montée consisting of 3 cylindrical cakes stacked on top of each other, all centered on the ( d ) axis as shown below : The three cylindrical cakes are the same height 10 cm . The largest cylindrical cake, the n o 1 , has radius 30 cm . The radius of the cake n o 2 is equal to 2 3 that of the cake n o 1 . The radius of the cake n o 3 is equal to 3 4 that of the cake n o 2 . 1 Show that the radius of the cake n o 2 is 20 cm . 2 Calculate the radius of the cake n o 3 . 3 Show that the exact total volume of the mounted piece is equal to 15 250 ı cm 3 . Reminder : the volume V of a cylinder of radius R and height h is given by the formula V = ı × R 2 × h . 4 What fraction of the total volume is the volume of the cake n o 2 ? Give the result as an irreducible fraction. E.6608 Below is a cylinder-shaped chocolate box: Its dimensions are: a height of 8 cm ; a diameter of 10 cm . To close this box, we use a rubber band that wraps around the box three times. On each turn, the rubber band passes through the centers of the two disks. Give the length of the rubber band when it is placed on the box in this way. 15. Quotient quantities and units E.4207 At the construction site of his future home, Mr. Dubois encounters a mason who seems to be having difficulty carrying a solid, cylindrical steel rod. This rod is 1.5 m long and has a base radius of 4 cm . 1 Calculate the volume of this figure rounded to the nearest cm 3 . 2 Steel has a density of 7.85 g = cm 3 . Calculate the mass of this rod rounded to kg . Hint: we will use : ı 3.142 E.9062 To build a well in his garden, Mr. Martin needs to buy 5 concrete cylinders like the one described below. She has room in her trailer for 5 cylinders, but she can only transport a maximum of 500 kg . Using the cylinder’s characteristics, determine the minimum number of trips M me Martin needs to make to transport his 5 cylinders with his trailer. Characteristics of a cylinder : inner diameter : 90 cm outer diameter : 101 cm height : 50 cm density of concrete : 2 400 kg = m 3 Determine the mass, rounded to the nearest kilogram, of con- https://chingmath.fr chapExoCorrec/7961 sacados/7961 (dno1no2no3 chapExoCorrec/6608 sacados/6608 chapExoCorrec/4207 sacados/4207 chapExoCorrec/9062 sacados/9062 Asie Juin 2019
1;70m 4;40m 7;5cm4cm12cm crete required for the design of this well. Reminder : volume of the cylinder = ı × radius × radius × height Indication : we will use : ı 3 ; 14 E.6309 A family of four is hesitating between two pool models. They are gathering information to help them make their decision. Information 1 : The two pool models : The ˇroundı pool Interior height : 1.20 m Top view: a circle with a ra-dius of 1.70 m The ˇoctagonalı pool Interior height : 1.20 m View from above : a regular polygon with an outer diame-ter of 4.40 m . Information 2 The construction of an above-ground pool with a surface area of less than 10 m 2 does not require any administrative proce-dures. Information 3 Recommended minimum surface area per swimmer : 3.40 m 2 . Information 4 Area of a regular octagon : A octogone = 2 2 × R 2 where R is the radius of the disk outside the octagon. Information 5 Flow rate of the filling tap : 12 liters of water per minute. Indication : we will use : ı 3.1416 1 Do any of the proposed models require administrative procedures? 2 The four members of the family want to swim at the same time. Explain why the family should choose the octagonal pool in this case. 3 We start filling this octagonal pool on Friday at 14 h 00 and leave the water running overnight until Saturday morning at 10 h 00 . Will the pool overflow? 16. Unclassified exercises E.4962 Below is the pattern of a cone of revolu-tion : Cut out the pattern, then build the cone of revolution. E.5691 In this exercise, if the work is not completed, leave a record of the research anyway. It will be taken into account in the assessment. A muffin pan (for baking) consists of 9 cavities. All of these cavities are iden-tical. Each cavity is shaped like a truncated cone (cone cut by a plane parallel to its base) shown opposite. The dimensions are shown in the figure opposite. Reminders: Volume of a cone with base radius r and height h : V = 1 3 × r 2 × ı × h 1 = 1 dm 3 Indications : we will use : ı 3 ; 1416 1 Show that the volume of a cavity is approximately 125 cm 3 . 2 Lea has prepared 1 liters of batter. She wants to fill each cavity of the mold to 3 4 of its volume. Does she have enough batter for the 9 cavities of the mold? Justify your answer. https://chingmath.fr chapExoCorrec/6309 sacados/6309 1;70m 4;40m chapExoCorrec/4962 sacados/4962 chapExoCorrec/5691 sacados/5691 Brevet - Asie Juin 2013 Correction Catherine Royer 7;5cm4cm12cm
Petitebasede20cmdediamètreGrandebasede46cmdediamètreHauteur:2500m ABO3cm AOS AOCK E.7962 The Rittershoffen geothermal power plant (Bas-Rhin) was in-augurated on June 7 2016 . A well was dug to capture hot water under pressure, at a depth of 2 500 m , at a temperature of 170 degrees Celsius. This well is shaped like the trun-cated cone shown opposite. The proportions are not to scale. Note: the volume of a truncated cone is calculatedâusing the following formula : V = ı 3 × h × R 2 + R × r + r 2 where h is the height of the truncated cone, R is the ra-dius of the larger base, and r is the radius of the smaller base. we will use : ı 3.1416 1 Check that the volume of the well is approximately equal to 225 m 3 . 2 The earth is compacted when it is in the ground. When it is extracted, it is no longer compacted and its volume increases by 30 % . Calculate the final volume of earth to be stored after drilling the well. E.5676 The figure below represents a solid com-posed of two cones of revolution sharing the same base disk, which has a radius of measure 3 cm . The distance AB measures 6 cm . Determine the volume of this solid rounded to the nearest cm 3 . Hint: we’ll use : ı 3.1416 E.4961 Consider the cone of revolution whose base radius is 4 cm and the hator measures 4 cm . A represen-tation of this solid is given below : Determine the volume, rounded to the nearest cubic centime-ter, of this cone of revolution. E.5440 Consider an hourglass made up of two identical cones of the same vertex C and whose base radius is AK =1.5 cm . To protect it, it is enclosed in a cylinder of height 6 cm and the same base as the two cones. 1 We note V the volume of the cylinder and V 1 the volume of the hourglass. All volumes will be expressed in cm 3 . a Show that the exact value of the volume V of the cylin-der is 13.5 ı . b Show that the exact value of V 1 is 4.5 ı . c What fraction of the volume of the cylinder does the volume of the hourglass occupy? (The result will be given as an irreducible fraction) . Reminder : the formula for the volume of the cone is : aire de la base × hauteur 3 2 We put 6 cm 3 of sand into the hourglass. Knowing that the sand will flow from one cone to another with a flow rate of 80 cm 3 = h , what time will be measured by this hourglass? https://chingmath.fr chapExoCorrec/7962 sacados/7962 Petitebasede20cmdediamètreGrandebasede46cmdediamètreHauteur:2500m chapExoCorrec/5676 sacados/5676 ABO3cm chapExoCorrec/4961 sacados/4961 AOS chapExoCorrec/5440 sacados/5440 AOCK