2011 AMC 10B 第 4 题

Question

LeRoy 和 Bernardo 一起进行了一周旅行，并同意平分费用。一周中，两人分别支付了一些共同费用，例如汽油和租车。旅行结束时，LeRoy 支付了

A

美元，Bernardo 支付了

B

美元，其中

A < B

。LeRoy 应给 Bernardo 多少美元，才能使两人平分费用？

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

A

dollars and Bernardo had paid

B

dollars, where

A < B.

How many dollars must LeRoy give to Bernardo so that they share the costs equally?

\dfrac{A + B}{2}

\dfrac{A - B}{2}

\dfrac{B - A}{2}

B - A

A + B

答案：C

知识点：代数变形平均数

难度评级：870

小提示：

比较 Bernardo 比 LeRoy 多付了多少。

Compare how much more Bernardo paid than LeRoy

大提示：

只需转移差额的一半。

Only half of the difference has to be transferred

解答：

两人每人应承担

\dfrac{A+B}2

，而 LeRoy 已支付

A

。因此他还需向 Bernardo 支付

\dfrac{A+B}2-A = \dfrac{B-A}2

美元。

所以正确答案是 C。

The amount they each would have to pay is

\dfrac{A+B}2,

and LeRoy paid

A.

Thus, he has to pay

\dfrac{A+B}2-A = \dfrac{B-A}2

more.

Thus, the correct answer is C .

2011 AMC 10B 第 4 题

答案：C

难度评级：870

小提示：

大提示：

解答：

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