Tính nhanh

A 490 × 365 - 390 × 365

24 × 6 + 6 × 70 + 36

B 365 × 96 + 365 × 3 + 365

24 × 12 - 24 - 24

`a)`

`490xx365-390xx365`

`=365xx(490-390)`

`=365xx100`

`=36500`

``

`24xx6+6xx70+36`

`=24xx6+6xx70+6xx6`

`=6xx(24+70+6)`

`=6xx100`

`=600`

``

`b)`

`365xx96+365xx3+365`

`=365xx(96+3+1)`

`=365xx100`

`=36500`

``

`24xx12-24-24`

`=24xx(12-1-1)`

`=24xx10`

`=240`