AMC 8 1989 Problem 1
AMC8 1989 年第 1 题
数列与规律★☆☆☆☆
题干整理中
- A.150
- B.199
- C.200
- D.249
- E.250
正确答案 · Correct Answer
E
解析 · Solution
Solution 1
Rearranging terms yields .
Alternatively, the terms can be arranged to get (1+9)+(11+19)+(21+29)+(31+39)+(41+49) = 10+30+50+70+90 = 250
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