Question

(1/4*1/7+1/7*1/10+1/10*1/13+1/13*1/16)*3= 简便算法

Answer 1

(1/4*1/7+1/7*1/10+1/10*1/13+1/13*1/16)*3

=[(1/3)*(1/4-1/7)+(1/3)*(1/7-1/10)+(1/3)*(1/10-1/13)+(1/3)*(1/13-1/16)]*3

=(1/3)*[(1/4-1/7)+(1/7-1/10)+(1/10-1/13)+(1/13-1/16)]*3

=(1/4)-(1/16)

=3/16