Question

What is the surface area of this right rectangular prism with dimensions of 5 centimeters by 5 centimeters by 12 centimeters?

Answer 1

Check the picture below.

so, the prism is just 6 rectangles stacked up to each other at the edges.

now, if we get the area of all 6, and sum them up, that's the surface area of the rectangular prism.

$\bf \stackrel{\textit{front and back}}{2(5\cdot 5)}~~+~~\stackrel{\textit{left and right}}{2(5\cdot 12)}~~+~~\stackrel{\textit{top and bottom}}{2(5\cdot 12)}$