1994 AMC 8 Problem 19

Attempt Problem 19 of the 1994 AMC 8 below, then check your answer against the professionally curated solution from LIVE by Po-Shen Loh. You can also try the full timed exam, view all 1994 AMC 8 solutions, or check the answer key.

All problems are used with official legal permission of the Mathematical Association of America (MAA).

19.

Around the outside of a 44 by 44 square, construct four semicircles with the four sides of the square as their diameters. Another square, ABCD,ABCD, has its sides parallel to the corresponding sides of the original square, and each side of ABCDABCD is tangent to one of the semicircles. The area of the square ABCDABCD is
1616
3232
3636
4848
6464
Answer: E
Concepts:square (geometry)circle
Small hint:
Each semicircle has a side of the 44 by 44 square as its diameter, so its radius is 22
Big hint:
A side of ABCDABCD equals the original side length plus two radii
Solution:
Each semicircle is built on a side of length 4,4, so its radius is 2.2. A semicircle bulges out from the middle of each side by that radius.
Each side of ABCDABCD is the original side plus two radii: 4+2(2)=8.4 + 2(2) = 8. So the area of ABCDABCD is 82=64.8^2 = 64.
Thus, the correct answer is E .
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