Tính nhanh 19x6+19x4 21x3+21x7

2 câu trả lời

`19` x `6+19` x `4`

`=19` x `(6+4)`

`=19` x `10`

`= 190`

`21` x `3+21` x  `7`

`=21` x `(3+7)`

`=21` x `10`

`=210`

 

$\text{19 $\times$ 6 + 19 $\times$ 4}$$\\$$\text{= 19 $\times$ (6 + 4)}$$\\$$\text{= 19 $\times$ 10 = 190}$$\\$$\text{21 $\times$ 3 + 21 $\times$ 7}$$\\$$\text{= 21 $\times$ ( 3 + 7 )}$$\\$$\text{= 21 $\times$ 10 = 210}$