AMC12 2000 A
AMC12 2000 A · Q3
AMC12 2000 A · Q3. It mainly tests Interest / growth (simple).
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?
每天，Jenny 吃掉当天开始时罐子里果冻豆的 $20\%$。第二天结束时，还剩 $32$ 颗。最初罐子里有多少颗果冻豆？
(A)
40
40
(B)
50
50
(C)
55
55
(D)
60
60
(E)
75
75
Answer
Correct choice: (B)
正确答案：（B）
Solution
We can begin by labeling the number of initial jellybeans $x$. If she ate $20\%$ of the jellybeans, then $80\%$ is remaining. Hence, after day 1, there are:
$0.8 * x$
After day 2, there are:
$0.8 * 0.8 * x$ or $0.64x$ jellybeans. $0.64x = 32$, so $x = \boxed{(B) 50}$
Solution By: armang32324
我们先设最初果冻豆的数量为 $x$。如果她吃掉了果冻豆的 $20\%$，那么剩下的是 $80\%$。因此，第 1 天后剩下：
$0.8 * x$
第 2 天后剩下：
$0.8 * 0.8 * x$ 或 $0.64x$ 颗果冻豆。由 $0.64x = 32$，得 $x = \boxed{(B) 50}$
Solution By: armang32324
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