用0,1,2,3,4,5六個(gè)數(shù)字組成無重復(fù)數(shù)字的五位數(shù),其中
(1)這樣的五位數(shù)的個(gè)數(shù)是___________;
(2)奇數(shù)有________個(gè),偶數(shù)有__________個(gè);
(3)5的倍數(shù)有________個(gè);
(4)奇數(shù)位必須為奇數(shù)有________個(gè).
解:
(1)首位特殊(首位不能為零):=600;
(2)末位,首位特殊(從未位入手):=288;
(3)可用(1)(2)的結(jié)論:600-288=312,也可分為末位是0,末位是2,4兩類,
末位是0:=120;末位是2,4: =192,共有120+192=312種;
(4)1,3,5位特殊:=36種.