1992 AMC 12 第 2 题

Question

一个瓮中装有硬币和珠子，每件物品不是银制就是金制。瓮中物品的百分之二十是珠子，硬币的百分之四十是银制的。金制硬币占瓮中全部物品的百分之几？

An urn is filled with coins and beads, all of which are either silver or gold. Twenty percent of the objects in the urn are beads. Forty percent of the coins in the urn are silver. What percent of the objects in the urn are gold coins?

40\%

48\%

52\%

60\%

80\%

答案：B

知识点：percent complementary percentage

难度评级：890

小提示：

先求硬币占全部物品的百分比

First find the percent of all objects that are coins

大提示：

再用银制硬币所占百分比的补数求金制硬币所占百分比

Of those coins, use the complement of the silver percentage

解答：

硬币占全部物品的

80\%

，其中

60\%

的硬币是金制的。因此金制硬币所占的比例为

0.80\cdot0.60=0.48=48\%\text{，}

这里是相对全部物品而言的。

因此正确答案是 B。

Coins make up

80\%

of the objects, and

60\%

of the coins are gold. Thus gold coins make up

0.80\cdot0.60=0.48=48\%

of all the objects.

Thus the correct answer is B.

1992 AMC 12 第 2 题

答案：B

难度评级：890

小提示：

大提示：

解答：

其他年份的第 2 题