8.由数字5,6,7,8,9可以组成多少个没有重复数字的四位奇数?
网友回答
要5,7,9 结尾即可.剩下4个数里选三个排列组合24x3=72
======以下答案可供参考======
供参考答案1:
5679/5689/5687/5689/5697/5769/5789/5867/5869/5879/5897/5967/5987/
6579/6587/6589/6587/6597/6759/6785/6789/6795/6875/6879/6857/6859/6895/6897/******
69个