GMAT 数学题（13）

sdcar2010 · 发表于 2011-1-7 10:29:10

N =1.25 × (0.05) × (0.0005) × (0.0025) × 20^m问 m 至少等于哪个正整数时，N 也是正整数？

sdcar2010 · 发表于 2011-1-21 04:48:23

.05 x .05 x .0005 x.0005 x 2^m x 10^m

If there are four 2's, then all the 5's in the above equation would be converted to 10's.
If there are either 10's, then all the 0's in the above equation would be converted to10's.

So m is at least 8 for N to be an integer.

Lyron · 发表于 2011-1-21 08:58:24

我算出来等于6 你算下

Lyron · 发表于 2011-1-21 09:01:12

你第二个式子和你第一个不同啊~ 我说的是第一个式子

sdcar2010 · 发表于 2011-1-21 09:49:30

LS, you are right. For the first formula, the answer is 6. For the second, 8. When I simplify, I made some mistakes. While 5 requires one 2, 25 requires two 2's.

qgirl · 发表于 2011-1-21 17:49:01

保持分数结构,不会乱

Lyron · 发表于 2011-1-21 17:57:27

是的

GMAT 数学题（13）

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