Question

F
is directly proportional to
a
.
If
F
=
25
when
a
=
5
find,
F
when
a
=
8

Answer 1

Since F and a are directly proportional, we can relate F to our unknown F, and a to our other known a.

25 / 5 = F / 8

Cross-multiply to solve.

5F = 200

F = 40

Hope this helps!