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