请列出用2、5、8、0这四个数字组成的所有四位数(数字可以重复使用)答:共有:3×4×4×4=192种 2000,2002,2005,2008,2020,2022,2025,2028,2050,2052,2055,2058,2080,2082,2085,2088,2200,2202,2205,2208,2220,2222,2225,2228,2250,2252,2255,2258,2280,2282,2285,2288,2500,2502,2505,2508,2520,2522,2525,2528,2550,2552,2555,2558,2580,2582,2585,2588,2800,...
2580,4个数字有多少种组合方法?答:2开头:2580,2508,2805,2850,2058,2085 5开头:5280,5208,5802,5820,5028,5082 8开头:8052,8025,8520,8502,8205,8250 0开头:0582,0528,0852,0825,0258,0285 共6*4=24种(不知道0开头算不。。不算的话就3*6=18种)