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标题: 请教OG11-86 [打印本页]

作者: redemptioner 时间: 2007-4-16 07:24 标题: 请教OG11-86

86.In an increasing sequence of 10 consecutive intergers, the sum of the first 5 integers is 560. What is the sum of the last 5 integers in the sequence?

A.585 B.580 C.575 D.570 E.565 答案A

算不出来，请大家帮忙，谢谢！

作者: assurance 时间: 2007-4-16 20:53

x,x+1,x+2,x+3,x+4,x+5,x+6,x+7,x+8,x+9.

x+(x+1)+(x+2)+(x+3)+(x+4)=560

(x+5)+(x+6)+(x+7)+(x+8)+(x+9)=560+5*25=585

作者: redemptioner 时间: 2007-4-17 20:11

thanks  a  lot @!!!!!!!!!

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