Question

Marla has a large white cube that has an edge of 10 feet. She also has enough green paint to cover 300 square feet. Marla uses all the paint to create a white square centered on each face, surrounded by a green border. What is the area of one of the white squares, in square feet?

$5\sqrt2$

$10$

$10\sqrt2$

$50$

$50\sqrt2$

Answer: D

Concepts:surface area cube geometry

Difficulty rating: 1070

Video solution:

Click to load, then click again to play

Written solution:

The total surface area is $6\cdot 10\cdot 10 = 600.$ Therefore, $600-300 = 300$ square feet aren't covered. This would be $\dfrac{300}{6} = 50$ square feet per face.

Thus, the answer is D .

2012 AMC 8 Problem 21

Answer: D

Difficulty rating: 1070

Video solution:

Written solution:

Problem 21 in Other Years