ayetha
幼苗
共回答了15个问题采纳率：80% 举报
1/6+1/24+1/60+1/120+1/210+1/336+1/112
=(1*1/6)+(1/4*1/6)+(1/6*1/10)+(1/6*1/20)+(1/6*1/35)+(1/6*1/56)+(1/2*1/56)
=(1/6)*(1+1/4+1/10+1/20+1/35)+1/56*(1/6+1/2)
=(1/6)*(140+35+14+7+4)/140+(1/56)*(2/3)
=(1/6)*200/140+1/84
=5/21+1/84
=21/84
=1/4
1年前
9
