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标题: prep數學題問 [打印本页]

作者: 狗狗007 时间: 2010-7-13 21:57
标题: prep數學題問
An investment of d dollars at k percent simple annual interest yields $600 interest over a 2-year period.In terms of d, what dollar amount invested at the same rate will yield $2,400 interest over a 3-year period?

(A) 2d/3

(B) 3d/4

(C) 4d/3

(D) 3d/2

(E) 8d/3

答案是E......不明白是怎麼做的......

作者: crazyxxx 时间: 2010-7-13 22:29
第一个式子:
2d*( 1+ k% ) = 600

设所求的值为n
3n*( 1+ k% ) = 2400
两个式子联立起来:
3n*( 1+ k% ) = 4 * 2 * d * ( 1 + k% )
n=8d/3

作者: zliycdr 时间: 2010-7-14 01:05
新版狗叔呼之欲出？

作者: 狗狗007 时间: 2010-7-14 22:59

新版狗叔呼之欲出？

-- by 会员 zliycdr (2010/7/14 1:05:57)

狗叔的definition是“堅持每道數學題都問么”？？

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