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Video: Finding the Lateral Surface Area of a Triangular Prism

Tim Burnham

Determine the lateral surface area of the given figure.


Video Transcript

Determine the lateral surface area of the given figure.

Now our given figure is a triangular prism, and our base or cross section is a triangle like this, which is repeated all the way through the prism. So when we’re asked for the lateral surface area, this means the total area of all the sides of our prism. So that’s this area plus this area plus this area. So that adds up to be three different rectangles that make up the sides of our prism.

Now we could work out the area of each rectangle individually, so 16 times 32, 30 times 32, and 34 times 32, and then add them together, which gives us a total of 2560. Now each of the individual links were in inches, so the area is in inches times inches; that’s inches squared or squared inches.

So our answer would be the lateral surface area is 2560 square inches, but there’s actually a slightly quicker way of doing the calculation. If I were to slide all of those rectangles together to make one big rectangle, the length of the longest side would be 16 plus 30 plus 34, which is 80 inches.

So when I work out the overall area of that rectangle, 80 times 32, I still get 2560 square inches. So if I’d worked out the perimeter of the base of our prism here and multiplied that by the length of the prism, I get the same answer, but it takes a bit less working out to do.