1×2分之一+2×3分之一+3×4分之一+4×5分之一+5×6分之一+6×7分之一？

1×1/2+2×1/3+3×1/4+4×1/5+5×1/6+6×1/7
=1/2+2/3+3/4+4/5+5/6+6/7
=1/2+1/3+1/3+1/4+2/4+1/5+3/5+1/6+4/6+6/7
=(1/2+1/3)+(1/3+1/4)+(1/5+1/6)+4/6+6/7+2/4+3/5
=5/6+7/12+11/30+4/6+6/7+0.5+0.6
=(35/60+22/60)+(5/6+4/6)+6/7+(0.5+0.6)
=57/60+9/6+6/7+1.1
=19/20+3/2+6/7+1.1
=0.95+1.5+1.1+6/7
=3.55+6/7
=71/20+6/7
=497/140+120/140
=617/140本回答被网友采纳