AMC8 2005

AMC8 2005 · Q1

AMC8 2005 · Q1. It mainly tests Linear equations, Fractions.

Connie multiplies a number by 2 and gets 60 as her answer. However, she should have divided the number by 2 to get the correct answer. What is the correct answer?

Connie 将一个数乘以 2，得到 60。但是，她本应该将这个数除以 2 才能得到正确答案。正确答案是什么？

(A) 7.5 7.5

(B) 15 15

(D) 120 120

(E) 240 240

Answer

Correct choice: (B)

正确答案：（B）

Solution

If $x$ is the number, then $2x=60$ and $x=30$. Dividing the number by $2$ yields $\dfrac{30}{2} = \boxed{\textbf{(B)}\ 15}$. A second way to do it is to divide the number by $4$, as you multiplied by $2$ when you were supposed to divide by $2$. So, $\dfrac{60}{4} = \boxed{\textbf{(B)}\ 15}$.

如果 $x$ 是这个数，那么 $2x=60$，从而 $x=30$。将这个数除以 $2$ 得到 $\dfrac{30}{2} = \boxed{\textbf{(B)}\ 15}$。另一种方法是将 60 除以 4，因为你本该除以 2 但却乘了 2。所以，$\dfrac{60}{4} = \boxed{\textbf{(B)}\ 15}$。

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