Question

F is directly proportional to a.
If F = 28 when a = 7 find,
F when a = 10

Answer 1

Explanation:

a=10

Step-by-step explanation:

The question can be interpreted as

F∝a

If we introduce proportionality constant k, we have

F= k.a

28= k. 7

k= 28/7

k= 4

Then the equation can be written as

F= 4.a

To find, a when F = 40?

F= 4.a

40=4 × a

a= 40/4

a= 10

Answer 2

F = 40

Explanation:

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

F = ka ← k is the constant of proportion

To find k use the condition F = 28 when a = 7 , then

28 = 7k ( divide both sides by 7 )

4 = k

F = 4a ← equation of proportion

When a = 10, then

F = 4 × 10 = 40