AMC8 1999

AMC8 1999 · Q17

AMC8 1999 · Q17. It mainly tests Rates (speed), Rounding & estimation.

Walter can buy eggs by the half-dozen. How many half-dozens should he buy to make enough cookies? (Some eggs and some cookies may be left over.) [Context: 108 students eat avg 2 cookies each, recipe 15 cookies/pan, 2 eggs/recipe]

Walter 可以按半打购买鸡蛋。他需要买多少半打鸡蛋才能做足够的饼干？（可能会有一些鸡蛋和饼干剩余。）[背景：108 名学生平均每人吃 2 块饼干，配方每盘 15 块饼干，每配方 2 个鸡蛋]

(A) 1 1

(B) 2 2

(D) 7 7

(E) 15 15

Answer

Correct choice: (C)

正确答案：（C）

Solution

Answer (C): One recipe makes $15$ cookies, so $216 \div 15 = 14.4$ recipes are needed, but this must be rounded up to $15$ recipes to make enough cookies. Each recipe requires $2$ eggs. So $30$ eggs are needed. This is $5$ half-dozens.

答案（C）：一份配方可以做 $15$ 块饼干，所以需要 $216 \div 15 = 14.4$ 份配方，但必须向上取整为 $15$ 份配方才能做够饼干。每份配方需要 $2$ 个鸡蛋，因此需要 $30$ 个鸡蛋。这相当于 $5$ 个半打。

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