1+ 1/2 +1/4 +1/8 +1/16 +1/32 +1/64
=1+(1-1/2)+(1/2-1/4)+(1/4-1/8 )+(1/8-1/16)+(1/16-1/32)+(1/32-1/64)
=2-1/64
=129/64