30 x 25 x 7 x 8 -------------------- 75 x 8 x 12 x 14

$\text{o Hnkn}$

Kiểu `1 :`

a)

`30 xx 25 xx 7 xx 8`

`= ( 25 xx 8 ) xx ( 30 xx 7 )`

`= 200 xx 210`

`= 42000`

b)

`75 xx 8 xx 12 xx 14`

`= ( 75 xx 8 ) xx ( 12 xx 14 )`

`= 600 xx 168`

`=28800`

Kiểu `2 :`

$\dfrac{30*25*7*8}{78*8*12*14}$

`=` $\dfrac{6*5*5*5*7*8}{6*13*8*6*2*7*2}$

`=` $\dfrac{5*5*5}{13*6*2*2}$

`=` $\dfrac{125}{312}$

( Dấu * là dấu nhân )