1/1×6+1/6×11+1/11×16+1/16×21+1/21×26等于几

题目

1/1×6+1/6×11+1/11×16+1/16×21+1/21×26等于几
简便运算

答案

1/1×6+1/6×11+1/11×16+1/16×21+1/21×26
=(1-1/6+1/6-1/11+1/11-1/16+1/16-1/21+1/21-1/26)/5
=(1-1/26)/5
=5/26