1-1/2+1/6+1/12+20/1.+1/72+1/90 1x2x3.x19x20问末尾有几个人零?

题目

1-1/2+1/6+1/12+20/1.+1/72+1/90 1x2x3.x19x20问末尾有几个人零?

答案

1-1/2+1/6+1/12+1/20.+1/72+1/90
=1-1/2+1/2-1/3+...+1/9-1/10
=1-1/10
=9/10
1x2x3.x19x20问末尾有20÷5=4,20÷125=0.20
4个零