# Surface Area of a Truncated Right Prism

I was studying for exams when I stumbled across this question.

A block of earth in the form of truncated right prism has a square base with 12 centimeter edges. Two adjacent lateral edges are each 20 centimeter long and the other two lateral edges are each 14 centimeter long. Find the total surface area of the block.

My work:

This is how I imagined the problem:

From here, I'm stuck.

I do know there are six areas found. I can find the area of the base, but I couldn't find the other 5 areas, in which two of those areas (the front and the back) has angled upper base. I don't know how to get those areas that involve angled upper bases.

How do you get the surface area of the above problem?

• Are the faces that have two equal sides trapezia? That is, are their other two edges parallel? – ajotatxe Aug 16 '17 at 15:37
• Your drawing is not a truncated prism. A right prism with a square base is basically a rectangular block. – Jaap Scherphuis Aug 16 '17 at 15:39
• Since it is a right prism the faces are perpendicular to the base not slanted. – marty cohen Aug 16 '17 at 15:41
• @JaapScherphuis oh gosh.......why do I mistake pyramids for prismsXD – Palautot Ka Aug 16 '17 at 15:42
• @ajotatxe my bad....I mistake pyramids for prisms – Palautot Ka Aug 16 '17 at 15:43