Grade 8
/ Other 9 exercises (including 3 corrected)
- The Pythagorean triplets (2 exercices)
- The square roots (1 exercice)
- The GPS system and triangulation (3 exercices)
EFG
member.
(Establish
the
equality
by
using
the
equality)
b
Determine
two
integers
a
and
b
such
that
:
50
=
a
2
×
b
c
Using
the
questions
2
et
4
,
establish
the
equality
in
another
way:
50
=
5
2
3.
The
GPS
system
and
triangulation
E.1344
The
only
instruments
allowed
are
a
ruler
and
a
compass
:
1
In
the
figure
below,
place
point
M
satisfying
the
follow-ing
conditions
:
EM
=
5
cm
;
FM
=
4
cm
;
GM
=
7
cm
2
Are
two
points
sufficient
to
perfectly
locate
the
position
of
a
third
point
in
the
plane?
Justify
your
answer.
Note:
la
Triangulation
by
measuring
distances
(or
trilateration)
allows
us
to
determine
the
exact
position
of
a
point
by
knowing
its
distance
from
other
points.
On
the
plane,
on
the
surface
of
the
earth,
at
least
three
points
are
needed
to
locate
a
point
exactly.
E.1346
Note:
Quartz
is
a
mineral
used
to
regulate
the
timing
of
all
modern
watches.
Quartz
is
obtained
from
silica,
which
has
piezoelectric
properties
discovered
by
Pierre
and
Jacques
Curie
in
1880.
Here
is
a
brief
description
of
the
piezoelec-tric
effect
:
When
subjected
to
mechanical
stress
(pressure,
stretch-ing)
,
it
develops
an
electric
field
;
When
subjected
to
an
electric
field,
quartz
undergoes
deformation.
The
first
property
is
used
in
particular
in
gas
lighters
:
when
a
button
is
pressed,
the
gas
lighter
creates
an
electric
arc.
The
second
property
is
used
in
mini-motors
(nanotechnol-ogy)
.
In
watches,
an
electronic
system
allows
these
two
properties
to
alternate
and
stabilizes
this
alternation
at
a
frequency
of
32
768
Hz
:
the
quartz
will
thus
vibrate
regularly
32
768
times
per
second.
Let
us
assume
four
objects
with
internal
clocks
set
to
the
same
time:
3
transmitters
(
E
,
F
,
G
)
and
1
receiver
(
R
)
.
It
is
assumed
that
the
waves
emitted
by
the
3
transmitters
propagate
at
the
speed
of
light,
which
is
3
×
10
8
m
=
s
(in
fact
299
792
458
m
=
s
)
.
The
receiver
R
is
set
to
the
same
time,
so
it
can
measure
the
time
taken
by
the
signal
from
each
transmitter.
Here
is
one
of
its
readings
:
Time
of
parcours
the
signal
Distance
actual
(in
cm
)
Distance
to
the
scale
(in
cm
)
from
E
to
R
0
;
0004
s
from
F
to
R
0
;
001
s
from
G
to
R
0
;
0017
s
1
Calculate
the
distance
between
point
M
and
each
of
the
receivers.
2
Here
are
points
E
,
F
,
G
shown
on
a
map
at
scale
1
=
6
000
000
https://chingmath.fr
chapExoCorrec/1344
sacados/1344
EFG
sacados/1346
EFG
S1S2O
RSEFGHIRSEFGHIPremier casSecond cas
SREFGHISREFGHITroisième casQuatrième cas
RST
Place
point
R
(construction
lines
must
remain
visible)
.
Note:
the
GPS
positioning
system
(Global
Positioning
Sys-tem)
consists
of
29
satellites
in
orbit.
Each
of
these
satellites
carries
an
atomic
clock
(see
box)
and
sends
a
signal
at
reg-ular
intervals
including
the
satellite’s
position
and
the
date
and
time
the
message
was
transmitted.
Quartz
clock
systems
have
a
margin
of
error
of
a
few
sec-onds
per
year,
while
atomic
clocks,
based
on
the
vibrational
properties
of
the
cesium
atom,
have
an
accuracy
of
a
few
seconds
per
million
years.
An
observer
O
located
on
Earth
receiving
signals
from
two
satel-lites
and
able
to
measure
the
dis-tance
between
themselves
and
these
satellites.
This
is
insuf-ficient
to
determine
their
exact
position
:
the
intersection
of
two
spheres
can
be
a
circle.
For
a
GPS
receiver
to
function
properly,
it
is
necessary
to
receive
signals
from
at
least
4
satellites
to
determine
its
po-sition
on
Earth.
E.1347
Here
are
four
figures
representing
the
same
points
R
and
S
and
a
contour
line
between
these
two
points.
1
Complete
the
following
table
:
In
each
case,
complete
the
following
table
:
RF
SF
RF
−
SF
RI
SI
RI
−
SI
1
o
2
o
3
o
4
o
Note:
Each
of
these
curves
represents
the
set
of
points
such
that
the
difference
in
distance
between
them
and
points
R
and
S
is
constant.
These
curves
are
called
hyperbolas,
and
points
R
and
S
are
called
the
foci
of
the
hyperbola.
These
curves
are
used
in
particular
to
determine
the
epicen-ter
of
an
earthquake
:
we
do
not
know
the
time
of
emission
of
the
seismic
waves,
but
we
can
measure
the
difference
in
the
arrival
time
of
the
signal
between
two
receivers.
In
this
case,
three
receivers
are
also
needed
to
determine
the
exact
position
of
the
emission
source.
3
Below
is
a
cross-section
of
the
earth,
where
points
R
,
S
,
and
T
represent
receivers
placed
on
the
earth’s
surface
:
We
know
that
:
https://chingmath.fr
EFG
S1S2O
sacados/1347
RSEFGHIRSEFGHIPremier casSecond cas
SREFGHISREFGHITroisième casQuatrième cas
RST
sssssssssssST
AgdeSèteMontpellierNîmesBalarucD31D31A927kmBalarucA990kmNîmesD3154kmNîmesD31A9Balaruc14km
123ABCDEFNombrededemi-journéesTarifATarifB183521640345
the
seismic
waves
arrived
at
receivers
R
and
S
at
the
same
time
while
the
signal
arrived
Δ=4
s
seconds
earlier
at
re-ceiver
S
than
at
receiver
T
.
Determine
the
exact
location
of
the
epicenter
F
of
the
earthquake.
4.
Unclassified
exercises
E.6336
Paul
wants
to
go
from
Agde
to
Montpel-lier.
He
has
two
choices
:
either
he
takes
the
highway
A9
,
or
he
takes
the
departmental
road
D31
.
Here,
diagrammed,
is
the
information
he
retrieves
from
a
map
:
1
He
estimates
that
he
is
averaging
110
km
=
h
on
the
highway
and
75
km
=
h
on
county
roads.
Which
route
should
he
take
to
get
to
the
city
of
Montpe-lier
the
fastest?
2
On
the
same
route,
Adeline
leaves
at
9
h
using
the
county
road
while
juliette
leaves
at
9
h
15
.
That
she
is
the
driver
who
will
arrive
in
Montpelier
the
soonest.
E.8945
An
association
offers
a
variety
of
activities
to
keep
children
occupied
during
the
school
vaca-tions.
Several
rates
are
offered
:
Rate
A
:
8
e
per
half
day;
Rate
B
:
a
membership
of
30
e
entitling
the
member
to
a
discounted
rate
of
5
e
per
half
day.
A
spreadsheet
file
has
been
prepared
to
calculate
the
cost
to
be
paid
based
on
the
number
of
half
days
of
activities
for
each
of
the
proposed
rates
:
Questions
1
,
2
,
4
,
and
5
do
not
require
justification.
1
Complete
this
table.
2
Find
from
the
following
answers
the
formula
that
was
entered
in
cell
B3
before
stretching
it
to
the
right
:
a
=8
×
B1
b
=30
×
B1+5
c
=5
×
B1+30
×
BA
d
=30+5
×
B1
e
=35
https://chingmath.fr
sssssssssssST
sacados/6336
AgdeSèteMontpellierNîmesBalarucD31D31A927kmBalarucA990kmNîmesD3154kmNîmesD31A9Balaruc14km
chapExoCorrec/8945
sacados/8945
123ABCDEFNombrededemi-journéesTarifATarifB183521640345
quandest cliquécachermettre la taille du stylo à1e∑acer toutaller à x:0y:0Rectangleajouter40àxajouter-20àyrépéter5foisde∏nir rectanglestylo en position d’écritures’orienter à90degrésavancer de40tournerde90degrésavancer de20tournerde90degrésrépéter2foisrelever le stylo
ajouter1à la taille du stylo
E.8898
We
want
to
make
a
frieze
com-posed
of
rectangles.
To
do
this,
we
wrote
the
program
below
:
Recall
that
the
instruction
ˇ
orient
to
90
ı
is
to
orient
horizon-tally
to
the
right.
In
this
exercise,
no
justification
is
required.
1
What
are
the
coordinates
of
the
starting
point
of
the
plot?
2
How
many
rectangles
are
drawn
by
the
main
script?
3
Draw
the
figure
obtained
with
the
main
script
freehand.
4
a
Without
modifying
the
main
script,
we
obtained
the
figure
below
composed
of
rectangles
of
length
40
pix-els
and
width
20
pixels.
Propose
a
modification
to
the
block
ˇ
rectangle
ı
that
would
result
in
this
figure.
b
Where
can
we
then
add
the
instruction
:
in
the
main
script
to
get
the
figure
below?
https://chingmath.fr
chapExoCorrec/8898
sacados/8898
quandest cliquécachermettre la taille du stylo à1e∑acer toutaller à x:0y:0Rectangleajouter40àxajouter-20àyrépéter5foisde∏nir rectanglestylo en position d’écritures’orienter à90degrésavancer de40tournerde90degrésavancer de20tournerde90degrésrépéter2foisrelever le stylo
ajouter1à la taille du stylo