Question

The variables a and b are proportional. When a=12 we

know b=3. What is the value of a when b=5?
O 17
9
20
O 14

Answer 1

b = 20

Explanation:

the variables a and b are proportional , so the equation relating them is

a = kb ← k is the constant of proportion

to find k use the condition a = 12 , b = 3

12 = 3k ( divide both sides by 3 )

4 = k

a = 4b ← equation of proportion

when b = 5 , then

a = 4 × 5 = 20