Question

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

Answer 1

F = 40

Explanation:

Given that F is directly proportional to a then the equation relating them is

F = ka ← k is the constant of variation

To find k use the condition F = 25 when a = 5, then

25 = 5k ( divide both sides by 5 )

5 = k

F = 5a ← equation of proportion

When a = 8, then

F = 5 × 8 = 40