2011 AMC 10B Problem 4

Attempt Problem 4 of the 2011 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 2011 AMC 10B solutions, or check the answer key.

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

4.

LeRoy and Bernardo went on a week-long trip together and agreed to share the costs equally. Over the week, each of them paid for various joint expenses such as gasoline and car rental. At the end of the trip it turned out that LeRoy had paid AA dollars and Bernardo had paid BB dollars, where A<B.A < B. How many dollars must LeRoy give to Bernardo so that they share the costs equally?

A+B2\dfrac{A + B}{2}

AB2\dfrac{A - B}{2}

BA2\dfrac{B - A}{2}

BAB - A

A+BA + B

Answer: C
Concepts:algebraic manipulationmean
Difficulty rating: 870
Solution:

The amount they each would have to pay is A+B2,\dfrac{A+B}2, and LeRoy paid A.A. Thus, he has to pay A+B2A=BA2\dfrac{A+B}2-A = \dfrac{B-A}2 more.

Thus, the correct answer is C .

← Problem 3#3
Full Exam

Problem 4 in Other Years