Question

Tính nhanh 
5/9 + 13/7 + 15/3 + 8/7 + 4/9 + 11/13

Answer 1

`5/9 + 13/7 + 15/3 + 8/7 + 4/9 + 11/13`

`= (5/9 + 4/9) + (13/7 + 8/7) + 5 + 11/13`

`= 9/9 + 21/7 + 5 + 11/13`

`=1 + 3 + 5 + 11/13`

`= 4 + 5 + 11/13`

`=9 + 11/13`

`=117/13 + 11/13`

`=(117 + 11)/13`

`=128/13`

Answer 2

5/9 + 13/7 + 15/3 + 8/7 + 4/9 + 11/13

= (5/9 + 4/9) + (13/7 + 8/7) + 5 + 11/13

= 1 + 3 + 5 + 11/13

= 9 + 11/13

= 117/13 + 11/13

= 128/13