2012 AMC 10B Problem 7

Attempt Problem 7 of the 2012 AMC 10B 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 2012 AMC 10B solutions, or check the answer key.

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7.

For a science project, Sammy observed a chipmunk and a squirrel stashing acorns in holes. The chipmunk hid 3 acorns in each of the holes it dug. The squirrel hid 4 acorns in each of the holes it dug. They each hid the same number of acorns, although the squirrel needed 4 fewer holes. How many acorns did the chipmunk hide?

30 30

36 36

42 42

48 48

54 54

Answer: D
Concepts:linear equationfraction
Difficulty rating: 1020
Solution:

Let the number of acorns they each hid be x.x. Then, the number of holes from the chipmunk is x3\dfrac x3 and the number of holes from the squirrel is x4.\dfrac x4 .

This means x3x4=x12=4\dfrac x3 - \dfrac x4 = \dfrac{x}{12}= 4 Therefore, x=48.x=48.

Thus, the correct answer is D .

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