Question

If y varies directly as x and y = 9 when x = –3, find y when x = 40.

Answer 1

y = -120

Explanation:

Direct variation is

y = kx where k is a constant

9 = k(-3)

Divide each side by -3

9/-3 = k

-3 = k

y = -3x

Let x = 40

y = -3(40)

y = -120