Help!!! I have to find the missing side link of a rectangular prism.

Question

My width is 20, the height is 12 and the total area/volume is 1,200. I need the L. Can you please help.

Answer 1

1) Start with the formula of a rectangular prism.

A = 2 * (WL + HL + HW)

This is the formula because you are finding the area of each of the different types of sides: WL, HL, and HW. But there are 6 sides of a rectangular prism, so you multiply it by 2.

2) If you have three components, you can find the fourth by plugging in.

1200 = 2 * (20L + 12L + (12*20)

3) Solve

1200 = 40L + 24L + (2*240)

1200 = 64L + 480

720 = 64L

L = 11.25