1/3+1/8+1/15+1/24……+1/360
=（1-1/3+1/2-1/4+1/3-1/5+1/4-1/6+……+1/18-1/20）÷2
=（1+1/2-1/19-1/20）÷2
=531/380÷2
=531/760