Question

A rectangular prism is 9.8 inches long, 20 inches wide, and 5 inches high. what is the surface area of the rectangular prism?

Answer 1

The prism has 6 faces: 2(length·width), 2(length·heighth), & 2(width·heighth)
2(length · width) = 2(9.8 · 20) = 2(196) = 392 in²
2(length · heighth) = 2(9.8 · 5) = 2(49) = 98 in²
2(width · heighth) = 2(20 · 5) = 2(100) = 200 in²

The sum of the faces is the surface area (S.A.)
 392 in² + 98 in² + 200 in² = 690 in²