1990 AMC 8 第 14 题
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所有题目均经美国数学协会（MAA）官方合法授权使用。
14.
一个袋子里只有蓝球和绿球。袋中有 个蓝球。如果从袋中随机取出一个球，取到蓝球的概率是 ，那么袋中有多少个绿球？
A bag contains only blue balls and green balls. There are blue balls. If the probability of drawing a blue ball at random from this bag is then the number of green balls in the bag is
小提示：
如果取到蓝球的概率是 ，那么蓝球占总数的四分之一
If the probability of blue is then blue balls are a quarter of the total
大提示：
用 个蓝球求出球的总数，再减去蓝球数得到绿球数
Use blue balls to find the total, then subtract to get the green balls
解答：
蓝球占袋中球总数的 ，而蓝球有 个，所以总数是 个。
绿球数为 。
所以正确答案是 B。
Since blue balls make up of the bag and there are of them, the total is balls.
So the number of green balls is .
Thus, the correct answer is B .
其他年份的第 14 题
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