2000 AMC 10 Problem 10

Below is the professionally curated solution for Problem 10 of the 2000 AMC 10, from LIVE by Po-Shen Loh. You can also try the full timed exam, view all 2000 AMC 10 solutions, or check the answer key.

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Concepts:triangle inequalitybounding to limit cases

Difficulty rating: 1370

10.

The sides of a triangle with positive area have lengths 4,4, 6,6, and x.x. The sides of a second triangle with positive area have lengths 4,4, 6,6, and y.y. What is the smallest positive number that is not a possible value of xy?|x - y|?

22

44

66

88

1010

Solution:

By the triangle inequality, each of xx and yy can be any number strictly between 64=26 - 4 = 2 and 6+4=10.6 + 4 = 10.

Then xy|x - y| can take any value with 0xy<8.0 \le |x - y| \lt 8.

The smallest positive number not attainable is 102=8.10 - 2 = 8.

Thus, the correct answer is D.

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