0-9可以组成哪些三位数答:100,101,102,103...109 201,202,203...209 301,302,303...309 110,111,112...119 210,211,212...以此类推.
0到9的所有数字排成3位数的有多少种,全排出来答:0不能排在百位,其他的任意排,总共有9*10*10=900种,100,101,102,103,104,105,106,107,108,109,110,111,112,113,114,115,116,117,118,119,120,121,122,123,124,125,126,127,128,129,130,131,132,133,134,135,136,137,138,139,140,141,142,143,144,145,146,147,148,149,150,...