Tính bằng cách thuận tiện nhất a) 3/7 x 5/6 + 5/6 x 4/7 = b) 4/9 x 5/6 - 1/3 x 4/9 = c) 1/6 : 4/5 + 1/8 : 4/5 = d) 1/6 : 4/5 - 1/8 : 4/5 =

Đáp án+Giải thích các bước giải:

`a) 3/7 xx 5/6 + 5/6 xx 4/7`

`= 5/6 xx (3/7+4/7)`

`= 5/6 xx 7/7`

`= 5/6 xx 1`

`= 5/6`

`b) 4/9 xx 5/6 - 1/3 xx 4/9`

`= 4/9 xx ( 5/6 - 1/3)`

`= 4/9 xx ( 5/6 - 2/6)`

`= 4/9 xx 3/6`

`= 4/9 xx 1/2`

`= 2/9`

`c) 1/6 : 4/5 + 1/8 : 4/5 `

`= ( 1/6 + 1/8) : 4/5`

`= ( 4/24 + 3/24) : 4/5`

`= 7/24 : 4/5`

`= 7/24 xx 5/4`

`= 35/96`

`d) 1/6 : 4/5 - 1/8 : 4/5`

`= (1/6-1/8) : 4/5`

`= (4/24-3/24) : 4/5`

`= 1/24 : 4/5`

`= 1/24 xx 5/4`

`= 5/96`