2010 AMC 10B Problem 8

Below is the professionally curated solution for Problem 8 of the 2010 AMC 10B, from LIVE by Po-Shen Loh. You can also try the full timed exam, view all 2010 AMC 10B solutions, or check the answer key.

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Concepts:greatest common divisorfactor counting

Difficulty rating: 1020

8.

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:

Note that xx must divide both 4848 and 64,64, which means that means it must divide their greatest common divisor.

The greatest common divisor of 4848 and 6464 is 16,16, which means xx divides 16.16.

1616 has 55 factors, namely all the powers of 22 up to 16.16.

Thus, E is the correct answer.

Problem 8 in Other Years