A geologist has a rock that is shaped like a rectangular pyramid that she would like to give as a gift. A model of the rock is shown.

A rectangular pyramid with base dimensions of 5 inches by 4 inches. The large triangular face has a height of 6.8 inches. The small triangular face has a height of 7 inches.

How much wrapping paper is needed without overlapping?

41 in2
68 in2
82 in2
102 in2

1 answer

To find the total surface area that needs to be wrapped, we need to find the area of each face of the rectangular pyramid and sum them up.

The base of the pyramid has a surface area of 5 * 4 = 20 square inches.
Each triangular face has a formula for finding its area - 0.5 * base * height. For the large triangular face: 0.5 * 5 * 6.8 = 17 square inches. For the small triangular face: 0.5 * 4 * 7 = 14 square inches.

Therefore, the total surface area that needs to be wrapped is 20 (base) + 17 (large face) + 14 (small face) = 51 square inches.

However, since wrapping paper doesn't cover only one side of the object, we need to multiply this by 2 to account for both the front and the back. So, 51 * 2 = 102 square inches.

Therefore, 102 square inches of wrapping paper is needed without overlapping. The closest answer choice is 102 in2.