Question

Y= 99
9. Suppose a varies directly as b, and a = 7 when b = 2. Find b when a = 21.

Answer 1

6

Explanation:

Given expression:

a varies directly as b;

a ∝ b

So;

a = kb where k is the constant of proportionality;

if a= 7 and b = 2;

7 = 2k

k =
`(7)/(2)`

Now, find b when a = 21

21 =
`(7)/(2)` x b

b = 6