Stacey needs to buy some cardboard to build a box 10 inches long, 9 inches wide, and 7 inches high. If she purchases 500 square inches of cardboard, how much will be left over?
446 square inches
54 square inches
426 square inches
406 square inches
The surface area of the box is calculated by finding the surface areas of all six sides and adding them together.
Surface area = 2lw + 2lh + 2wh
Surface area = 2(10*9) + 2(10*7) + 2(9*7)
Surface area = 420 square inches
If Stacey purchases 500 square inches of cardboard, and the surface area of the box is 420 square inches, she will have 500 - 420 = 80 square inches of cardboard left over.
So the answer is 80 square inches.