Question

一个罐子里有 $5$ 种不同颜色的软糖。 $30\%$ 是蓝色， $20\%$ 是棕色， $15\%$ 是红色， $10\%$ 是黄色，另外 $30$ 颗是绿色。如果把一半蓝色软糖换成棕色软糖，那么会有多少颗棕色软糖？

A jar contains $5$ different colors of gum drops. $30\%$ are blue, $20\%$ are brown, $15\%$ are red, $10\%$ are yellow, and the other $30$ gum drops are green. If half of the blue gum drops are replaced by brown gum drops, how many gum drops will be brown?

$\ 35$

$\ 36$

$\ 42$

$\ 48$

$\ 64$

答案：C

知识点：百分数

难度评级：1200

解答：

绿色所占百分比是 $100\%$ 减去其他颜色百分比之和： $100\%-30\%-20\%-$ $15\%-10\% = 25\%$

因为 $30$ 颗绿色软糖是总数的 $25\%$ ，所以软糖总数为 $\dfrac { 30}{.25} = 120$ 。

一开始棕色软糖有 $.2\cdot120 = 24$ 颗，蓝色软糖有 $.3\cdot120 = 36$ 颗。把一半蓝色换成棕色会增加 $\dfrac{36}{2} = 18$ 颗棕色软糖。因此棕色软糖共有 $24+18= 42$ 颗。

所以正确答案是 C。

Since we have percentages for every color except green, the percent of green is $100\%$ minus the sum of the other colors. This would make the percent of green equal to $100\%-30\%-20\%-$ $15\%-10\% = 25\%$

Since we know $30$ gum drops is $25\%,$ we know that the total number of gum drops is $\dfrac { 30}{.25} = 120.$

This means there are $.2\cdot120 = 24$ brown gum drops to start and $.3\cdot120 = 36$ blue gum drops. If half of the blue gum drops are turned to brown, then $\dfrac{36}{2} = 18$ more brown gum drops are added. Therefore, we have $24+18= 42$ brown gum drops.

Thus, the answer is C .

2010 AMC 8 第 15 题

答案：C

难度评级：1200

解答：

其他年份的第 15 题