Description: Sal explains how to find the volume of a rectangular prism fish tank that has fractional side lengths. Created by Sal Khan. Mario has a fish tank that is a right rectangular prism with base 15.6 centimeters by 7.2 centimeters. Since it's a fish tank, let me actually do it in blue. So this is the base right over here, so let me draw this.*Teacher Advisor is 100% free.