- Lateral surface (4 exercices)
- Volume expansion and reduction (4 exercices)
- Pyramid, enlargement, reduction, affine functions (1 exercice)
ABCDS
SADCBABCDSADCBOADCBO
ABCDHS
ABCDHSMNOP
a
Give
the
volume
V
of
the
pyramid
ABCDO
and
the
volume
V
of
the
pyramid
EFGHO
.
b
Give
the
value
of
the
ratio
V
V
of
the
volumes.
E.6299
Paul
visiting
Paris
admires
the
Pyramid,
made
of
laminated
glass
in
the
center
of
the
Louvre’s
inner
courtyard.
This
regular
pyramid
has
:
base
a
square
ABCD
side
35
meters
;
for
height
the
segment
[
SO
]
of
length
22
meters.
Paul
enjoyed
the
pyramid
so
much
that
as
a
souvenir
of
his
visit
he
bought
an
oil
lamp
whose
glass
reservoir
is
a
scale
reduction
1
500
of
the
real
pyramid.
The
lamp’s
instructions
state
that,
once
lit,
it
burns
4
cm
3
of
oil
per
hour.
After
how
long
will
there
be
no
oil
left
in
the
reservoir?
Round
off
to
the
nearest
hour.
Reminder
:
Volume
of
a
pyramid
=
one-third
of
the
product
of
the
area
of
the
base
times
the
height.
Show
the
approach
used
on
the
copy.
Any
trace
of
research
will
be
taken
into
account
during
assessment
even
if
the
work
is
not
completely
finished.
E.987
An
hourglass
consists
of
two
super-imposed
pyramids,
as
shown
in
the
sketch
below.
The
sand
flows
at
point
S
.
The
surface
of
the
sand
is
represented
by
the
plane
A
B
C
D
horizontal
and
parallel
to
the
bases
of
the
pyramids
SABCD
The
pyramid
SABCD
is
regular,
its
base
is
a
square
ABCD
,
recall
that
the
height
(
SO
)
is
perpendicular
to
the
plane
ABCD
.
The
sand
level
is
marked
by
the
length
SA
on
the
pyramid
edge
SABCD
.
We
give
:
OA
=27
mm
et
SO
=120
mm
.
Throughout
this
problem,
A
is
the
middle
of
[
SA
]
.
1
Represent
the
base
ABCD
in
full
size.
2
a
Justify
that
the
triangle
AOB
is
isosceles
rectangle.
b
Show
that
:
AB
=27
2
mm
3
a
Calculate
the
area
of
the
square
ABCD
b
Deduce
the
volume
V
of
the
pyramid
SABCD
is
58
320
mm
2
4
The
triangle
SOA
is
right-angled.
Show
that
:
SA
=
123
mm
.
5
Pyramid
SA
B
C
D
is
a
reduction
of
the
SABCD
pyra-mid.
a
What
can
we
say
about
the
straight
lines
(
OA
)
and
(
O
A
)
?
b
Determine
the
coefficient
of
reduction
SO
SO
.
6
Note
V
the
volume
of
the
pyramid
SA
B
C
D
.
Calculer
V
.
7
It
is
assumed
that
the
volume
of
sand
lowered
is
propor-tional
to
the
time
elapsed.
all
the
sand
runs
out
in
4
minutes.
After
how
long
is
the
sand
level
in
the
position
studied?
E.5920
A
regular
pyramid
with
vertex
S
has
base
ABCD
square
such
that
its
volume
V
is
equal
to
108
cm
3
.
Its
height
measures
9
cm
.
The
volume
of
a
pyramid
is
given
by
the
relationship
:
Volume
of
a
pyramide
=
aire
of
the
base
×
hauteur
3
1
Verify
that
the
area
of
ABCD
is
36
cm
3
.
Deduce
the
value
of
AB
.
Show
that
the
perimeter
of
the
triangle
ABC
is
equal
to
12+6
2
cm
.
2
SMNOP
is
a
reduction
of
the
pyramid
SABCD
.
We
then
obtain
the
pyramid
SMNOP
such
that
the
area
of
the
square
MNOP
is
equal
to
4
cm
2
a
Calculate
the
volume
of
the
pyramid
SMNOP
.
b
For
this
question,
any
trace
of
research,
however
incomplete,
will
be
taken
into
account
in
the
evaluation
.
Elise
thinks
that
to
obtain
the
perimeter
of
the
triangle
MNO
,
we
simply
divide
the
perimeter
of
the
triangle
ABC
by
3
.
Do
you
agree
with
her?
https://chingmath.fr
sacados/6299
ABCDS
chapExoCorrec/987
sacados/987
Afrique de l'ouest et Asie - juin 2005 - 12 points
SADCBABCDSADCBOADCBO
sacados/5920
ABCDHS
ABCDHSMNOP
SABCDEFGH
SABCDMNPQ
3.
Pyramid,
enlargement,
reduction,
affine
functions
E.991
In
the
figure
opposite,
SABCD
is
a
square-based
pyramid
of
height
[
SA
]
such
that
:
AB
=9
cm
;
SA
=12
cm
.
The
triangle
SAB
is
right-angled
at
A
.
First
part
EFGH
is
the
section
of
the
pyramid
SABCD
by
the
plane
parallel
to
the
base
and
such
that
:
SE
=3
cm
.
1
a
Calculate
EF
.
b
Calculate
SB
.
2
a
Calculate
the
volume
V
of
the
pyramid
SABCD
.
b
Give
the
reduction
coefficient
to
go
from
pyramid
SABCD
to
pyramid
SEFGH
.
c
Deduce
the
volume
V
of
SEFGH
.
A
value
rounded
to
unity
will
be
given.
Second
part
Let
M
be
a
point
of
[
SA
]
such
that
SM
=
x
cm
,
where
x
is
between
0
and
12.
We
call
MNPQ
the
section
of
the
pyramid
SABCD
by
the
plane
parallel
to
the
base
passing
through
M
.
1
Show
that
:
MN
=0.75
·
x
2
Let
A
(
x
)
be
the
area
of
the
square
MNPQ
as
a
function
of
x
.
Show
that
:
A
(
x
)=0.5625
·
x
2
.
3
Complete
the
table
below
:
Longueur
x
(en
cm
)
0
2
4
6
8
10
12
Area
A
(
x
)
of
the
square
MNPQ
4
Draw
a
reference
frame
where
:
on
the
x-axis,
1
cm
represents
1
unit
;
on
the
ordinate
axis,
1
cm
represents
10
units.
the
x-axis
and
y-axis
are
perpendicular.
Place
in
this
frame
the
points
with
abscissa
x
and
ordi-nate
A
(
x
)
given
by
the
table.
5
Is
the
area
of
MNPQ
proportional
to
the
length
SM
?
Justify
using
the
graph.
https://chingmath.fr
chapExoCorrec/991
sacados/991
Paris - Juin 2006 - 12 points
SABCDEFGH
SABCDMNPQ