Question

If y varies directly as x and y = 5 when x = 12, find y when x = 4.

Answer 1

y = 15

Explanation:

y varies directly as x.

⇒y = kx where k is a constant.

find k:

when x = 4, y = 5

5 = k(4)

5 = 4k

k = 5/4

plug k into the equation:

y = 5/4 k

find y when x = 12:

when x = 12:

y= 5/4(12)

y = 5(3)

y = 15