Question

1+1/2-5/6+7/12-9/20+11/30-13/42+15/56-17/72等于多少？儿子的作业，谢谢

请讲解的清楚一点，小孩子要能看懂的。

Answer 1

1+1/2-5/6+7/12-9/20+11/30-13/42+15/56-17/72
=1+1/2-(1/2+1/3)+(1/3+1/4)-……+（1/7+1/8）-(1/8+1/9)
=1+1/2-1/2-1/3+1/3+1/4+……+1/7+1/8－1/8－1/9
=1-1/9
=8/9

Answer 2

1+1/2-5/6+7/12-9/20+11/30-13/42+15/56-17/72
=1+1/2-(1/2+1/3)+(1/3+1/4)-……+（1/7+1/8）-(1/8+1/9)
=1+1/2-1/2-1/3+1/3+1/4+……+1/7+1/8－1/8－1/9
=1-1/9
=8/9