Question

求解数学题求用数字0.1.3.5.7可组成多少个三位数[个位上的数字允许重复】?

Answer 1

假设不能用零开头,

C(5,3)*P(3,3)-C(4,2)*P(2,2)=10*6-6*2=48个

103,130,310,301,105,150,510,501

107,170,710,701,305,350,530,503

307,370,730,703,507,570,750,705

135,153,315,351,513,531,

137,173,317,371,713,731,

157,175,517,571,715,751

357,375,537,573,735,753.