GMAT 数学题（5）

supermanlee

在 0 和 1000 之间的正整数中，有多少个奇数其每个数位上的数字都不一样？
1) 310
2) 330
3) 365
4) 400
5) 415

And why?

supermanlee

365 is the right answer!  

#1: you are on the right track.  Just need to figure out a way to quickly calculate the possibilities than to count them by hand.

#2 and #3 are using different methods to solve this question.  Brilliant!