2014 AMC 10A Problem 19

Below is the professionally curated solution for Problem 19 of the 2014 AMC 10A, from LIVE by Po-Shen Loh. You can also try the full timed exam, view all 2014 AMC 10A solutions, or check the answer key.

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Concepts:3D geometrydistance formulasimilarity

Difficulty rating: 1790

19.

Four cubes with edge lengths 1,1, 2,2, 3,3, and 44 are stacked as shown. What is the length of the portion of XY\overline{XY} contained in the cube with edge length 3?3?

3335\dfrac{3\sqrt{33}}5

232\sqrt3

2333\dfrac{2\sqrt{33}}3

44

323\sqrt2

Solution:

The distance between XX and YY with respect to the zz-axis is 1+2+3+4=10. 1 + 2 + 3 + 4 = 10.

Both the distances along the xx and yy-axes are 4.4.

Then XY=42+42+102=233. XY = \sqrt{4^2 + 4^2 + 10^2} = 2\sqrt{33}.

Let the desired length be x.x. Then using similar triangles, we have that x3=23310 \dfrac{x}{3} = \dfrac{2\sqrt{33}}{10} x=3335. x = \dfrac{3\sqrt{33}}{5}.

Thus, A is the correct answer.

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