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

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