(1/8+1/24+1/48+1/80+1/120+1/168+1/224)*64=?简便算法

问题描述:

(1/8+1/24+1/48+1/80+1/120+1/168+1/224)*64=?
简便算法

(1/8+1/24+1/48+1/80+1/120+1/168+1/224)*64
=(1/2-1/4+1/4-1/6+....+1/14-1/16)/2*64
=(1/2-1/16)*32
=5/16*32
=10

观察单项:1/8=(1/2-1/4)/21/24=(1/4-1/6)/21/48=(1/6-1/8)/21/80=(1/8-1/10)/21/120=(1/10-1/12)/21/168=(1/12-1/14)/21/224=(1/14-1/16)/2提出来1/2;括号内很容易求和;即:(1/2-1/16)*64/2=16-2=14...