Question

一加仑油漆用来粉刷一个房间。第一天用了全部油漆的三分之一。第二天用了剩余油漆的三分之一。原来油漆的几分之几可以在第三天使用？

A gallon of paint is used to paint a room. One third of the paint is used on the first day. On the second day, one third of the remaining paint is used. What fraction of the original amount of paint is available to use on the third day?

$\dfrac{1}{10}$

$\dfrac{1}{9}$

$\dfrac{1}{3}$

$\dfrac{4}{9}$

$\dfrac{5}{9}$

答案：D

知识点：分数比与比例

难度评级：870

解答：

第一天之后，剩下 $1 - \dfrac13 = \dfrac23$ 的油漆。

第二天用掉原来总量的 $\dfrac13 \cdot \dfrac23 = \dfrac29$ 。

第三天可用的部分为 $\dfrac23 - \dfrac29 = \dfrac49.$

所以正确答案是 D。

After the first day, $1 - \dfrac13 = \dfrac23$ of the paint remains.

On the second day, $\dfrac13 \cdot \dfrac23 = \dfrac29$ of the original amount is used.

The fraction available on the third day is $\dfrac23 - \dfrac29 = \dfrac49.$

Thus, D is the correct answer.

2005 AMC 10B 第 3 题

答案：D

难度评级：870

解答：

其他年份的第 3 题