1951 AMC 12 第 8 题

Question

一件商品的价格降低了

10\%

。要恢复原价，降价后的价格必须增加：

The price of an article is cut

10\%.

To restore it to its former value, the new price must be increased by:

10\%

9\%

11\dfrac19\%

11\%

以上答案均不正确

None of these answers

知识点：百分数

降价后，价格是原价的

90\%

After the cut, the price is

90\%

of the original

若所需的增幅为

p

，求解

0.9(1+p)=1

If the required increase is

p

, solve

0.9(1+p)=1

设原价为

1

。降价后的价格为

0.9

。所需的增幅为

\frac{1-0.9}{0.9}=\frac19\text{，}

即

11\dfrac19\%

。

因此，正确答案是 C。

Let the original price be

1.

The reduced price is

0.9.

The required fractional increase is

\frac{1-0.9}{0.9}=\frac19,

which is

11\dfrac19\%.

Thus, the correct answer is C.

其他年份的第 8 题