Question

1,tính bằng cách thuận tiện nhất :

a,245*5*4

b,2*125*4*5

c,357*36+357*64

d,542*68-28*542.

ai làm nhanh nhất mình k cho.

Answer 1

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

Answer 2

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

Answer 3

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

Answer 4

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