a,245 x 5 x 4=245x(5x4)=245x20=4900
b,2x125x4x5=(2x5)x(125x4)=10x500=5000
c,357x36+357x64=357x(36+64)=357x100=35700
d,542x68-28x542=542x(68-28)=542x40=21680
Hok tốt
a) 245 x 5 x 4
= ( 245 x 4 ) x 5
= 980 x 5
= 4900
b) 2 x 125 x 4 x 5
= ( 125 x 4 ) x ( 2 x 5 )
= 500 x 10
= 5000
c) 357 x 36 + 357 x 64
= 357 x ( 36 + 64 )
= 357 x 100
= 35700
d) 542 x 68 - 28 x 542
= 542 x ( 68 - 28 )
= 542 x 40
= 21680
245*5*4=5*5*4*49=25*4*49=100*49=4900
2*125*4*5=8*125*5=1000*5=5000
357*36+357*64=357*(36+64)=357*100=35700
542*68-28*542=542*(68-28)=542*20=542*2*10=1084*10=10840
a)245x5x4=49x5x4x5=49x(5x5)x4=49x(25x4)=49x100=4900
b)2x125x4x5=2x5x25x4x5=(2x5)x(25x4)x5=10x100x5=1000x5=5000
c)357x36+357x64=357x(36+64)=357x100=35700
c)542x68-28x542=542x(68-28)=542x40=21680