1973 AMC 12 第 7 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。
7.
介于 与 之间、末位数字为 的所有整数之和为
The sum of all the integers between and which end in is
小提示：
这些整数构成从 到 的等差数列
The integers form an arithmetic sequence from through
大提示：
用公差求项数，再把首项与末项配对
Use the common difference to count the terms, then pair the first and last
解答：
该数列为 它共有 项。因此它的和为
所以正确答案是 A。
The sequence is It has terms. Its sum is therefore
Therefore, the correct answer is A.
其他年份的第 7 题
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