2005 AMC 8 第 12 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。
12.
大艾尔这只猩猩从五月 日到五月 日一共吃了 根香蕉。他每天都比前一天多吃六根。大艾尔在五月 日吃了多少根香蕉？
Big Al, the ape, ate bananas from May through May Each day he ate six more bananas than on the previous day. How many bananas did Big Al eat on May
小提示：
五天的数量形成等差数列
The five daily amounts form an arithmetic sequence.
大提示：
中间那天等于五天的平均数
The middle day equals the average of the five days.
解答：
设大艾尔在五月 日吃了 根香蕉。那么从五月 日开始，五天的数量为
它们的和为 ，等于 。所以 。于是五月 日大艾尔吃了 根香蕉。
所以正确答案是 D。
Let be the number of bananas Big Al ate on May Then Big Al ate the following amounts starting from May
The sum of this is which equals This gives us that Then on May Big Al ate bananas.
Thus, D is the correct answer.
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