2014 AMC 12B Problem 5

Below is the professionally curated solution for Problem 5 of the 2014 AMC 12B, from LIVE by Po-Shen Loh. You can also try the full timed exam, view all 2014 AMC 12B solutions, or check the answer key.

All of the real AMC 8, AMC 10, AMC 12, and AIME problems in our complete solution collection are used with official legal permission of the Mathematical Association of America (MAA).

Concepts:ratio and proportionlinear equationrectangle

Difficulty rating: 1400

5.

Doug constructs a square window using 88 equal-size panes of glass, as shown. The ratio of the height to width for each pane is 5:2,5 : 2, and the borders around and between the panes are 22 inches wide. In inches, what is the side length of the square window?

2626

2828

3030

3232

3434

Solution:

Let each pane have width 2x2x and height 5x.5x. The window is 44 panes wide with 55 vertical borders, so its width is 4(2x)+52=8x+10.4(2x) + 5\cdot2 = 8x+10.

It is 22 panes tall with 33 horizontal borders, so its height is 2(5x)+32=10x+6.2(5x) + 3\cdot2 = 10x+6.

Setting width equal to height gives 8x+10=10x+6,8x+10 = 10x+6, so x=2x=2 and the side length is 102+6=26.10\cdot2+6 = 26.

Thus, the correct answer is A.

Problem 5 in Other Years