2015 AMC 10A 第 1 题

Question

求下列表达式的值。

(2^0-1+5^2+0)^{-1} \times 5

What is the value of the following expression?

(2^0-1+5^2+0)^{-1} \times 5

-125

-120

\dfrac{1}{5}

\dfrac{5}{24}

25

先计算括号内的值。

Evaluate inside the parentheses first

化简括号后，取倒数再乘以

5

。

After simplifying the parentheses, multiply its reciprocal by

5

可以这样计算。

\begin{aligned} &(2^0-1+5^2+0)^{-1} \times 5 \\&=\dfrac{1}{1 - 1 + 25} \times 5 \\ &= \dfrac{5}{25}\\ &= \dfrac{1}{5} \end{aligned}

所以正确答案是 C。

We can evaluate it as follows.

\begin{aligned} &(2^0-1+5^2+0)^{-1} \times 5 \\&=\dfrac{1}{1 - 1 + 25} \times 5 \\ &= \dfrac{5}{25}\\ &= \dfrac{1}{5} \end{aligned}

Thus, C is the correct answer.

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