Grade 9 / Algorithms 15 exercises (including 0 corrected)

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quandest cliquécacher la variablexcacher la variableydemanderChoisis un nombreet attendremettrexàréponsemettreyàx*x-9direEn choisissantpendant1secondedireréponsependant1secondedireOn obtientpendant1secondedirey quandest cliquedemanderChoisis un nombreet attendremettrexàréponsedireJe multiplie le nombre par6pendant2secondesmettreEtape 1à×6xdireJ’ajoute 10 au résultatpendant2secondesmettreEtape 2à+Etape 110direJe divise le résultat par 2pendant2secondesmettreRésultatà/Etape 22direregroupeJ’obtients ∏nalementResultatCréer une variableEtape 1Etape 2Résultatx 1. Simple algorithm E.7617 The figure below is a screenshot of a program made with ˇ Scratch ı software: 1 Show that if we choose 2 as the starting number, then the program returns 5 . 2 What does the program return if we choose at the start : a the number 5 ? b the number 4 ? 3 Determine the numbers that must be chosen initially for the program to return 0 . E.7611 Consider the computational pro-gram shown here in which x , Step 1 , Step 2 and Résultat are four variables : 1 a Julie ran this program by choosing the number 5 . Verify that what it says at the end is ˇ I finally get 20 ı b What does the program say if Julie runs it by initially choosing the number 7 ? 2 Julie runs the program, and what it says at the end is ˇ I finally get 8 ı. What name did Julie choose at the begin-ning? 3 If we call x the number chosen at the beginning, write as a function of x the expression we get at the end of the program, and then reduce that expression as much as possible. 4 Maxime uses the calculation program below : Choose a number. Add 2 to it. Multiply the result by 5 . Can we choose a number for which the result obtained by Maxime is the same as the result obtained by Julie? 2. Algorithm and repetition https://chingmath.fr sacados/7617 quandest cliquécacher la variablexcacher la variableydemanderChoisis un nombreet attendremettrexàréponsemettreyàx*x-9direEn choisissantpendant1secondedireréponsependant1secondedireOn obtientpendant1secondedirey sacados/7611 quandest cliquedemanderChoisis un nombreet attendremettrexàréponsedireJe multiplie le nombre par6pendant2secondesmettreEtape 1à×6xdireJ’ajoute 10 au résultatpendant2secondesmettreEtape 2à+Etape 110direJe divise le résultat par 2pendant2secondesmettreRésultatà/Etape 22direregroupeJ’obtients ∏nalementResultatCréer une variableEtape 1Etape 2Résultatx
s’orienter à90 quandest cliquée∑acer toutaller à x:-200y:-100s’orienter à90Mettrecôtéà100triangleavancer decôtéAjouter àcôté-20répéter5fois123457896 dé∏nir trianglestylo en position écritureavancer decôtétournerde120degrésrépéter3foisrelever le stylo123456 tournerde60degrés Figure 1Figure 2Figure 3 quandest cliquécacheraller à x:0y:0s’orienter à90degrésmettrelongueurà90e∑acer toutmettre la taille du stylo à3stylo en position d’écritureun tourajouter àlongueur30répéter2foisDé∏nir un touravancer delongueurtournerde90degésrépéter2foisajouter àlongueur30avancer delongueurtournerde90degrésrépéter2fois s’orienter à90degrés E.7615 The following program is given that draws several equilateral triangles of different sizes. This program has a variable named ˇ side ı. The lengths are given in pixels. Recall that the instruction means moving to the right. 1 What are the coordinates of the starting point of the plot? 2 How many triangles are drawn by the script? 3 a What is the length (in pixels) of the side of the sec-ond drawn triangle? b Freehand draw the look of the figure obtained when this script is run. 4 We modify the original script to obtain the figure below : State the number of a statement in the script after which can be placed : to get this new figure. E.7618 Here are three different figures, none of which are to the scale shown in the exercise: The program below contains a variable named ˇ length ı. Recall that the instruction means to move to the right with the pen. 1 a Draw the figure obtained with the block ˇ one turn ı given in the right frame above, for a starting length equal to 30 , being oriented to the right with the pen, at the beginning of the plot. We will take 1 cm for 30 units of length, i.e. 30 pixels. b How are we oriented with the pen after this plot? (no justification is required) . 2 Which of the figures 1 or 3 does the above program pro-duce? Justify your answer. https://chingmath.fr sacados/7615 s’orienter à90 quandest cliquée∑acer toutaller à x:-200y:-100s’orienter à90Mettrecôtéà100triangleavancer decôtéAjouter àcôté-20répéter5fois123457896 dé∏nir trianglestylo en position écritureavancer decôtétournerde120degrésrépéter3foisrelever le stylo123456 tournerde60degrés sacados/7618 Figure 1Figure 2Figure 3 quandest cliquécacheraller à x:0y:0s’orienter à90degrésmettrelongueurà90e∑acer toutmettre la taille du stylo à3stylo en position d’écritureun tourajouter àlongueur30répéter2foisDé∏nir un touravancer delongueurtournerde90degésrépéter2foisajouter àlongueur30avancer delongueurtournerde90degrésrépéter2fois s’orienter à90degrés
quandestcliquécachermettrelatailledustyloà2alleràx:-240y:0e∑acertoutstyloenpositionécritures’orienterà90maisonavancerde20répéternfoisde∏nirmaisontournerde90degrésavancerde50tournerde45degrésavancerde50tournerde90degrésavancerde50tournerde45degrésavancerde50tournerde90degréstracédela"maison".d CMHEA30oCeschéman’estpasenvraiegrandeur dé∏nir carréstylo en position écritureavancer delongueurtournerde90degrésrépéter4foisrelever le stylo quandest cliquémettrelongueurà10carrémettrelongueuràlongueur+20répéter4foiscacherProgramme no1 quandest cliquémettrelongueurà10carrémettrelongueuràlongueur*2répéter4foiscacherProgramme no2 Dessin no1Dessin no2Dessin no3 E.7613 For a ˇ rue ı, we defined the layout of a ˇmaisonı. 1 Check that d is approximately equal to 71 to the nearest unit. 2 A point in your program’s execution window has its ab-scissa that can vary from 240 to 240 and its ordinate that can vary from 180 to 180 . What is the largest, integer n that can be used in the main program to make the ˇrueı plot fit in your com-puter window o where the prgram runs? You can draw on your copy all the diagrams (freehand or not) that have been used to answer the previous ques-tion and add any useful information (values, encodings, additional features, point names. . . ) 3 Please note, this question is independent of the pr{ecédentes questions and the ˇ maison ı is slightly dif-ferent. If you want to add a chimney outlet to the layout of the house to make it more realistic, you need to do a mini-mum of calculations to avoid any surprises. Examples : It is assumed that : points H , E and A are aligned ; points C , M and A are aligned ; [ CH ] and [ EM ] are perpendicular to [ HA ] ; AM = 16 MC = 10 HAC = 30 o Calculate EM , HC and HE in order to get a nice chim-ney exit. E.7619 The instruction block ˇ square ı opposite has been programmed and then used in the two programs below : The instruction ˇ move forward by 10 ı moves the sprite forward by 10 pix-els. 1 Here are three drawings : a Which of these three drawings do you get with the program n o 1? b Which of these three drawings do we obtain with the program n o 2? c For each of the two programs, determine the lengths, in pixels, of the side of the largest square drawn? 2 We wish to modify the program n o 2 to obtain the draw-ing below : Which of the following three modifications produces the desired drawing? No justification is required for this question. https://chingmath.fr sacados/7613 quandestcliquécachermettrelatailledustyloà2alleràx:-240y:0e∑acertoutstyloenpositionécritures’orienterà90maisonavancerde20répéternfoisde∏nirmaisontournerde90degrésavancerde50tournerde45degrésavancerde50tournerde90degrésavancerde50tournerde45degrésavancerde50tournerde90degréstracédela"maison".d CMHEA30oCeschéman’estpasenvraiegrandeur sacados/7619 dé∏nir carréstylo en position écritureavancer delongueurtournerde90degrésrépéter4foisrelever le stylo quandest cliquémettrelongueurà10carrémettrelongueuràlongueur+20répéter4foiscacherProgramme no1 quandest cliquémettrelongueurà10carrémettrelongueuràlongueur*2répéter4foiscacherProgramme no2 Dessin no1Dessin no2Dessin no3
Modi∏cation1quandestcliquémettrelongueurà10carréavancerdelongueur+10mettrelongueuràlongueur*2répéter4foiscacherModi∏cation2quandestcliquémettrelongueurà10carrémettrelongueuràlongueur*2avancerdelongueur+10répéter4foiscacherModi∏cation3quandestcliquémettrelongueurà10carrémettrelongueuràlongueur*2répéter4foisavancerdelongueur+10cacher Pointdedépart6030o150o dé∏nir Losangestylo en position d’écritureavancer detournerde30degrésavancer detournerde150degrésavancer detournerdedegrésavancer detournerdedegrésrelever le stylo s’orienter à90degrés quandest cliquée∑acer toutaller à x:0y:0s’orienter à90degrésrépéter12fois tournerde30degrés losange tournerde150degrés avancer de600 Profondeurd’unemarcheHauteurd’unemarche E.7620 1 We’d like to draw the diamond-shaped pattern below. Complete the Losange block script to obtain this pattern. The pattern Losange Le block Losange 2 We want to make the figure below constructed from the Losange block completed in question 1 . Remember that the instruc-tion means we’re heading to the right. From the instructions below, indicate on your copy, in or-der, the two instructions to be placed in the loop opposite to finish the script. a b c d E.10683 We want to make a wooden stair-case of height 272 cm . The height of a step is 17 cm . The depth of a step for placing the foot measures 27 cm . 1 How many steps should be built? 2 We write the program below with Scratch software to de-sign this staircase. ( 1 cm in reality is represented by 1 by in the program.) Copy lines 5 , 6 , 7 and 9 , completing them. 3. Algorithm and conditional E.7614 We consider the following calcula-tion program : Choose a number; Multiply it by 4 ; Add 5 to the result. 1 Verify that when we choose 2 with this program, we https://chingmath.fr Modi∏cation1quandestcliquémettrelongueurà10carréavancerdelongueur+10mettrelongueuràlongueur*2répéter4foiscacherModi∏cation2quandestcliquémettrelongueurà10carrémettrelongueuràlongueur*2avancerdelongueur+10répéter4foiscacherModi∏cation3quandestcliquémettrelongueurà10carrémettrelongueuràlongueur*2répéter4foisavancerdelongueur+10cacher sacados/7620 Pointdedépart6030o150o dé∏nir Losangestylo en position d’écritureavancer detournerde30degrésavancer detournerde150degrésavancer detournerdedegrésavancer detournerdedegrésrelever le stylo s’orienter à90degrés quandest cliquée∑acer toutaller à x:0y:0s’orienter à90degrésrépéter12fois tournerde30degrés losange tournerde150degrés avancer de600 sacados/10683 Profondeurd’unemarcheHauteurd’unemarche sacados/7614
quandest cliquédemanderChoisir un nombreet attendresi-4×réponse+5<0alorsdireBravodireEssaie encoresinon OChat quandestcliquéDépartQuandπèchegaucheestcliquéajouter-40àxQuandπèchedroiteestcliquéajouter80àxQuandπèchehautestcliquéajouter80àyQuandπèchebasestcliquéajouter-40àyQuandn’importequoiestcliquédireJet’aiattrapépendant2secondesDépartSiBalletouchéealors get 13 . 2 What number should we choose at the start to get 3 ? 3 Salome has the following script run : a What will the sprite’s answer be if she chooses the number 12 ? b What will be the sprite’s answer if she chooses the number 5 ? 4 The above calculation program can be translated into the literal expression 4 · x +5 with x representing the chosen number. Solve the following inequation : 4 · x +5 < 0 5 Under what condition, pertaining to the chosen number, is it certain that the sprite’s answer will be ˇ Bravo ı? 4. Event programming E.7612 The image below shows the position obtained when the start block of a game program is triggered. The background is made up of dots spaced 40 units. In this position, the cat’s coordi-nates are ( 120 ; 80) . The object of the game is to position the cat on the ball. 1 What are the coordinates of the center of the ball shown in this position? 2 In this question, the cat is in the position obtained when the start block is triggered. Here’s the script for the ˇ chat ı moving sprite. a Explain why the cat does not return to its starting po-sition if the player presses the key and then the key. b The player presses the following succession of keys : c Which of the following key sequence proposals allows the cat to reach the ball? Move 1 Move 2 Move 3 →→→→→→→↑↑↑↑↑ →→→↑↑↑→↑← ↑←↑←↑←←↓↓ 3 What happens when the cat hits the ball? https://chingmath.fr quandest cliquédemanderChoisir un nombreet attendresi-4×réponse+5<0alorsdireBravodireEssaie encoresinon sacados/7612 OChat quandestcliquéDépartQuandπèchegaucheestcliquéajouter-40àxQuandπèchedroiteestcliquéajouter80àxQuandπèchehautestcliquéajouter80àyQuandπèchebasestcliquéajouter-40àyQuandn’importequoiestcliquédireJet’aiattrapépendant2secondesDépartSiBalletouchéealors
quandestcliquéinitialisationquandπechehautestcliqués’orienterà0styloenpositiond’écritureavancerde50releverlestyloquandπechedroiteestcliqués’orienterà90styloenpositiond’écritureavancerde50releverlestyloquandπechebasestcliqués’orienterà180styloenpositiond’écritureavancerde50releverlestylo initialisation s’orienter à9090 à droite-90 à gauche0 vers le haut180 vers le bas Dessin 1Dessin 2Dessin 3 quandestcliquéinitialisationquandπechehautestcliqués’orienterà0styloenpositiond’écritureavancerde50releverlestyloquandπechedroiteestcliqués’orienterà90avancerde50quandπechebasestcliqués’orienterà180styloenpositiond’écritureavancerde50releverlestylo FHCible-100-50050100-100-5050100 E.7616 Margot has written the following program. It allows to draw with three keys of the keyboard. For information This block erases the pre-vious drawing, posi-tions the pen to the left of the screen, and raises the pen. 1 Of the following three designs, only one will not be pos-sible with this program. Which one? Explain. 2 Julie has modified Margot’s program (see below) . What then does drawing 3 become with Julie’s modified pro-gram? 5. Unclassified exercises E.7965 Throughout the exercise, the unit of length is the mm . A dart is thrown at a square plate with a circular target (gray in the figure) . If the point of the dart is on the edge of the target, the target is considered not hit. This experiment is considered random and we are interested in the probability that the dart hits the target. the length of the square plate side is 200 . the radius of the target is 100 . the dart is represented by the point F of coordinates ( x ; y ) where x and y are random numbers between 100 and 100 . 1 In the example above, the dart F is located at the coor-dinate point (72 ; 54) . Show that the distance OF , between the dart and the origin of the reference frame is 90 . 2 Generally speaking, what number must not exceed the distance OF for the dart to hit the target? 3 A program is made that simulates throwing this dart at the square plate several times and counts the number of throws hitting the target. The programmer has cre-ated three variables named : square OF , distance and score . https://chingmath.fr sacados/7616 Asie Juin 2017 4 points quandestcliquéinitialisationquandπechehautestcliqués’orienterà0styloenpositiond’écritureavancerde50releverlestyloquandπechedroiteestcliqués’orienterà90styloenpositiond’écritureavancerde50releverlestyloquandπechebasestcliqués’orienterà180styloenpositiond’écritureavancerde50releverlestylo initialisation s’orienter à9090 à droite-90 à gauche0 vers le haut180 vers le bas Dessin 1Dessin 2Dessin 3 quandestcliquéinitialisationquandπechehautestcliqués’orienterà0styloenpositiond’écritureavancerde50releverlestyloquandπechedroiteestcliqués’orienterà90avancerde50quandπechebasestcliqués’orienterà180styloenpositiond’écritureavancerde50releverlestylo sacados/7965 FHCible-100-50050100-100-5050100
quandestcliquémettrescoreà0alleràx:nombrealéatoireentre-100et100y:nombrealéatoireentre-100et100mettreCarrédeOFàabscissex*abscissex+mettredistanceàracinedeajouteàscore1Sidistance<...alorsrépéter120fois Pointdedépartdutracé quandest cliqués’orienter à90e∑acer toutstylo en position d’écritureavancer de80tournerde144degrésavancer de80tournerde72degrésrépéterfoisrelever le stylo s’orienter à90 avancer de80tournerde144degrésavancer de80tournerde72degrésrépéterfois a When running this program, how many throws are sim-ulated? b What is the role of the variable score ? c Complete and copy on the copy only the 5 , 6 , and 7 lines of the program so that it works correctly. d After one run of the program, the variable score is equal to 102 . How often was the target reached in this simulation? Express the result as an irreducible fraction? 4 Assume that the probability of hitting the target is equal to the quotient : area of the target divided by area of the square plate. Give a value of this probability approximated to the near-est hundredth. E.7968 Arthur has to write a program with Scratch to draw a star like the draw-ing shown opposite. His program is missing the number of repetitions. Programme commencé par Arthur Information The instruction means moving to the right 1 What number must he enter in the double ˇ repeat ı to get the star? 2 Determine the perimeter of this star. 3 Arthur wishes to enlarge this star to obtain a star whose perimeter would be double, by modifying his program. Copy the part of the pro-gram opposite onto the copy, modifying the val-ues required to obtain this new star. https://chingmath.fr quandestcliquémettrescoreà0alleràx:nombrealéatoireentre-100et100y:nombrealéatoireentre-100et100mettreCarrédeOFàabscissex*abscissex+mettredistanceàracinedeajouteàscore1Sidistance<...alorsrépéter120fois sacados/7968 Asie Juin 2018 Pointdedépartdutracé quandest cliqués’orienter à90e∑acer toutstylo en position d’écritureavancer de80tournerde144degrésavancer de80tournerde72degrésrépéterfoisrelever le stylo s’orienter à90 avancer de80tournerde144degrésavancer de80tournerde72degrésrépéterfois
quandest cliquéaller à x:0y:0stylo en position d’écritures’orienter à90degrémettreLongueurà 300CarréTriangleavancer deLongueur/6mettreLongueuràCarréTriangle Dé∏nir Carréavancer deLongueurtournerde90degrésrépéter4fois Dé∏nir Triangleavancer deLongueurtournerde120degrésrépéter3fois quandest cliquédemanderChoisissez un nombreet attendreenvoyer à tousle nombre a été saisimettreNombreàréponsemettreRésultat 1à2*Nombre+3mettreRésultat 1àRésultat 1*Résultat 1direregroupele résultat 2 estRésultat 2 quand je reçoisle nombre a été saisimettreRésultat 2àNombre*NombremettreRésultat 2àRésultat 2*4mettreRésultat 2àRésultat 2+12*NombremettreRésultat 2àRésultat 2+9attendre3secondedireregroupele résultat 2 estRésultat 2 le résultat 2 est9 E.7969 The lengths are in pixels. The expression ˇ orienting at 90 ı means orienting to the right. The following program is given : 1 We take 1 cm as the scale for 50 pixels. a Show on your copy the figure obtained if the program is run up to and including the line 7 . b What are the coordinates of the pen after line 8 is ex-ecuted? 2 We run the full program and get the figure below that has a vertical axis of symmetry. Copy and complete the 9 line of the program to obtain this figure. 3 a Which of the following transformations, translation, homothety, rotation, symmetry, axial, is the geometric transformation that yields the small square from the large square? Specify the reduction ratio. b What is the ratio of areas between the two squares drawn? E.7974 Here is a script entered by Alice in an algorithmic software. 1 Alice chose 3 as her number, calculate the values of ˇ Re-sult 1 ı and ˇ Result 2 ı? Justify by showing the calculations made 2 Generalization: a Calling x the number chosen in the algorithm, give a literal expression translating the first part of the algo-rithm corresponding to ˇ Result 1 ı. b Calling x the number chosen in the algorithm, give a literal expression translating the second part of the algorithm corresponds to ˇ Result 2 ı. c Find the number or numbers chosen by Alice that match the result shown below : https://chingmath.fr sacados/7969 quandest cliquéaller à x:0y:0stylo en position d’écritures’orienter à90degrémettreLongueurà 300CarréTriangleavancer deLongueur/6mettreLongueuràCarréTriangle Dé∏nir Carréavancer deLongueurtournerde90degrésrépéter4fois Dé∏nir Triangleavancer deLongueurtournerde120degrésrépéter3fois sacados/7974 quandest cliquédemanderChoisissez un nombreet attendreenvoyer à tousle nombre a été saisimettreNombreàréponsemettreRésultat 1à2*Nombre+3mettreRésultat 1àRésultat 1*Résultat 1direregroupele résultat 2 estRésultat 2 quand je reçoisle nombre a été saisimettreRésultat 2àNombre*NombremettreRésultat 2àRésultat 2*4mettreRésultat 2àRésultat 2+12*NombremettreRésultat 2àRésultat 2+9attendre3secondedireregroupele résultat 2 estRésultat 2 le résultat 2 est9