1/(1*4)+1/(4*7)+1/(7*10)...+1/(91*94) 简算法算

问题描述:

1/(1*4)+1/(4*7)+1/(7*10)...+1/(91*94) 简算法算

=1/3×[(1-1/4)+(1/4-1/7)+(1/7-1/10)+……+(1/91-1/94)]
=1/3×[1-1/94]
=1/3×93/94
=31/94