Question

Jenny 每天吃掉当天开始时罐子里软糖的 $20\%$ 。第二天结束时还剩 $32$ 颗。罐子里原来有多少颗软糖？

Each day, Jenny ate $20\%$ of the jellybeans that were in her jar at the beginning of that day. At the end of the second day, $32$ remained. How many jellybeans were in the jar originally?

$40$

$50$

$55$

$60$

$75$

答案：B

知识点：百分数逆推法

难度评级：1080

解答：

每天吃掉 $20\%$ ，所以每天结束时剩下 $80\%$ 。若原来有 $x$ 颗，则 $(0.8)^2 x = 32.$

解得 $0.64x = 32$ ，所以 $x = 50$ 。

因此，正确答案是 B。

Since $20\%$ is eaten each day, $80\%$ remains at the end of each day. If $x$ is the original number, then $(0.8)^2 x = 32.$

Solving gives $0.64x = 32,$ so $x = 50.$

Thus, the correct answer is B.

2000 AMC 12 第 3 题

答案：B

难度评级：1080

解答：

其他年份的第 3 题