2010 AMC 12B Problem 3

Below is the professionally curated solution for Problem 3 of the 2010 AMC 12B, from LIVE by Po-Shen Loh. You can also try the full timed exam, view all 2010 AMC 12B solutions, or check the answer key.

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Concepts:greatest common divisorfactor counting

Difficulty rating: 1010

3.

A ticket to a school play costs xx dollars, where xx is a whole number. A group of 99th graders buys tickets costing a total of $48,48, and a group of 1010th graders buys tickets costing a total of $64.64. How many values for xx are possible?

11

22

33

44

55

Solution:

The price xx must divide both totals, so xx is a common divisor of 4848 and 64.64.

Since gcd(48,64)=16,\gcd(48,64)=16, the common divisors are 1,2,4,8,1, 2, 4, 8, and 16.16. There are 55 possible values.

Thus, the correct answer is E.

Problem 3 in Other Years