Question

If y varies directly as x, and y=7 when x=3, find when x=7

Answer 1

Direct variation means the ratio of y to x is constant.

y1/x1 = y2/x2 ⇒

y2 = (x2/x1) y1

Plug in

x1 = 3

y1 = 7

x2 = 7

and get y2.