1+1/2+1/3+2/3+1/4+2/4+3/4+1/5+2/5+3/5+4/5+……+1/60+2/60……59/60

题目

1+1/2+1/3+2/3+1/4+2/4+3/4+1/5+2/5+3/5+4/5+……+1/60+2/60……59/60
急需,速度啊!

答案

1/n+2/n+3/n+……+(n-1)/n
=[1+2+……+(n-1)]/n
=[n(n-1)/2]/n
=(n-1)/2
所以原式=1+1/2+2/2+3/2+……+59/2
=1+(1+2+……+59)/2
=1+59*60/2/2
=886