Transcript The dimensions of a rectangular solid are 3 inches by 4 inches by 5 inches.

The dimensions of a rectangular solid are 3 inches by 4 inches by 5 inches. The length
of each edge of the solid is to be increased by 20%. What is the surface area, in
square inches, of the new solid?
(a)
86.4
(b)
94
(c)
112.8
(d)
135.4
(e)
162.4
Correct Answer: D
Explanation:
If the length of each edge is increased by 20%, then the area of each face of the new
solid is increased by 44% (1.2l x 1.2w = 1.44lw, where l and w represent the
dimensions of a face). The surface area of the original solid is equal to 2[(3 x 4) + (3 x
5) + (4 x 5)] = 94 square inches. Thus, the surface area of the new solid is equal to
1.44 x 94 = 135.36 square inches, which rounds to 135.4. The correct answer is D
.
Another way to solve the problem is to find the lengths of each edge of the new solid
by multiplying the length of each edge by 1.2 and then compute the surface area. The
dimensions of the new solid are 3.6 inches by 4.8 inches by 6 inches, so the surface
area is equal to 2[(3.6 x 4.8) + (3.6 x 6) + (4.8 x 6)] = 135.36 square inches.