The length of a hollow pipe is three times its radius.

Other · Multi-part · AoPS · Mathematics · One-Variable Linear Equations · Linear Equations in Disguise

Problem

The length of a hollow pipe is three times its radius. (1) Write an expression for its outer surface area in terms of its radius

r

. (2) If the outer surface area is

301.6 \text{ m}^2

, find the radius of the pipe.