Question

1-1/6 7/12-9/20 11/30-13/42 15/56-17/72 19/90

Answer 1

我很想回答你提的问题，但不知你写的这些是啥意思，每个人看了都不明白你的目的是什么，我给你的答案是8个X。

Answer 2

1-1/6 +7/12-9/20 +11/30-13/42 +15/56-17/72 +19/90
=1-(1/2-1/3)+(1/3+1/4)-(1/4+1/5)+(1/5+1/6)-(1/6+1/7)+(1/7+1/8)-(1/8+1/9)+(1/9+1/10)
=1-1/2-1/3+1/3+1/4-1/4-1/5+1/5+1/6-1/6-1/7+1/7+1/8-1/8-1/9+1/9+1/10
=1-1/2+1/10
=1/2+1/10
=6/10
=3/5。

Answer 3

1-1/6=5/6
7/12-9/20=35/60-27/60=8/60=2/15
11/30-13/42=77/210-65/210=

Answer 4

简便计算
裂项法:
1-5/6 十7/12-9/20十 11/30-13/42十 15/56-17/72十 19/90
=1一1/2一1/3十1/3十1/4一1/4一1/5十1/5十1/6一1/6一1/7十1/7十1/8一1/8一1/9十1/9十1/10
=1/2十1/10
=3/5