Question

简便计算:1/2+3/4+7/8+15/16+31/32+63/64+127+218

Answer 1

最后一项应该是"127/128"..

然后原式=(1-1/2)+(1-1/4)+(1-1/8)+(1-1/16)+(1-1/32)+(1-1/64)+(1-1/128)=7-(1/2+1/4+1/8+1/16+1/32+1/64+1/128)=7-1/2[1-(1/2)^7]/(1-1/2)=769/128.