In this specific case
,we have two proportional values
x
(
c
e
n
t
i
m
e
t
e
r
s
)
and
y
(
m
i
l
e
s
)
that have a variation in directly proportional form
.
So we have:
x
1
=
2
c
m
y
1
=
68
m
i
l
e
s
x
2
=
7
c
m
y
2
=
?
m
i
l
e
s
Since
,
x
and
y
vary directly
, then
, when
x
increases it also
increases
y
. For this reason
, it must be satisfied that:
y
2
x
2
=
y
1
x
1
So if we do cross - multiplying:
y
2
⋅
x
1
=
y
1
⋅
x
2
Now
, solving for
y
2
:
y
2
=
y
1
⋅
x
2
x
1
So
, substituting the given values:
y
2
=
68
×
7
2
=
238
m
i
l
e
s
Therefore
,
7
c
m
represent 238 miles
.