计算:1/6+1/12+1/20+1/30+1/42+1/56+1/72(提示:1/6=1/2X3,1/12=1/3X4,1/20=/14X5)
问题描述：
计算:1/6+1/12+1/20+1/30+1/42+1/56+1/72(提示:1/6=1/2X3,1/12=1/3X4,1/20=/14X5)
上面提示最后一个打错了，下面是正确的
计算:
1/6+1/12+1/20+1/30+1/42+1/56+1/72(提示:1/6=1/2X3,1/12=1/3X4,1/20=1/4X5)
答
那你就拆开呀,这样前后可以约掉,
1/6+1/12+1/20+1/30+1/42+1/56+1/72
=(1/2-1/3)+(1/3-1/4)+(1/4-1/5)+(1/5-1/6)+(1/6-1/7)+(1/7-1/8)+(1/8-1/9)
=1/2-1/9
=7/18