Posted by aleasha on .
i know the formula of a rectangles surface area is SA= 2(lw)+(wh)+(lh), but when the dimensions are : 2a for the height, a for the width, and 3a for the length, how do i solve?

math (surface area) 
MathMate,
Put l=3a, w=a, h=2a
into your formula to get
S = 2(lw+wh+lh)
= 2(3a*a + a*2a + 3a*2a)
= 2(11a²)
= 22a²
Check my work.
Bote: The parentheses in your formula have been misplaced. The correct form is:
S=2(lw+wh+lh)