1/8+1/24+1/80+1/120的简便算法.当天答对给分.x*[12/(12+18)]+(14-x)*[9/(9+3)]=14*(1/2)
问题描述：
1/8+1/24+1/80+1/120的简便算法.
当天答对给分.
x*[12/(12+18)]+(14-x)*[9/(9+3)]=14*(1/2)
答
解析：
原式=（1/240）*（30+10+3+2）=（1/240）*45=45/240=3/16
答
1/8+1/24+1/80+1/120
=1/8+1/24+1/48+1/80+1/120-1/48
=1/2(1/2-1/4)+1/2(1/4-1/6)+1/2(1/6-1/8)+1/2(1/8-1/10)+1/2(1/10-1/12)-1/48
=1/2(1/2-1/12)-1/48
=3/16
答
1/8+1/24+1/80+1/120
=（1/8+1/80）+（1/24+1/120）
=11/80+1/20
=15/80
=3/16