a: =234x(45+54+1)

=234x100

=23400

b: =(8x125)x(50x20)

=1000x1000

=1000000

a = 243x(45+54+1)

=243 x 100

=24300

b = (20 x 50 ) x (8x125)

=1000x1000

=1000000

a) 234 x 45 + 54 x 234 + 234

= 234 x (45+54+1) = 234 x 100 = 23400

b) 50 x 8 x 125 x 20 = (50 x 20) x (8 x 125)

= 1000 x 1000 = 1000000

243 x 25 x 3 x 4

= ( 243 x 3 ) x ( 25 x 4 )

= 729 x 100

= 72900

= ( 234 x 4 ) x ( 25 x 4 )

= 936 x 100

= 93600

a) 234 + 567 + 766 + 433

= (234 + 766) + (567 + 433)

= 1 000 + 1 000

= 2 000

b) 2 023 + 7 602 - 1 023 + 1 398

= (2 023 - 1 023) + (7 602 + 1 398)

= 1 000 + 9 000

= 10 000

c) 4 789 - 2 567 - 7 433 + 5 211

= (4 789 + 5 211) - (2 567 + 7 433)

= 10 000 - 10 000

= 0

c, 5 - 10 + 15 - 20 + 25 - 30 + 35 - 40 + 50 - 55 + 60 - 65 + 70

= 5 + (15 - 10) + (25 - 20) + (35 - 30) + (50 - 40) + (60 - 55) + (70 - 65)

= 5 + 5 + 5 + 5 + 10 + 5 + 5

= (5 + 5) + (5 + 5) + 10 + (5 + 5)

= 10 + 10 + 10 + 10

= 10 $\times$ 4

= 40

a,   234 + 567 + 766 + 433

= (234 + 766) + (567 + 433)

= 1000 + 1000

= 2000

b, 2023 + 7602 - 1023 + 1398

= (2023 - 1023) + (7602 + 1398)

= 1000 + 9000

= 10000

c, 4789 - 2567 - 7433 + 5211

= (4789 + 5211) - (2567 + 7433)

= 10000 - 10000

= 0

d, 5 - 10 + 15  - 20 + 25 - 30 + 35 - 40 + 50 - 55 + 60 - 65 + 70

= (70 -65) + (60 - 55) +(50 - 40) + (35  - 30) + (25 - 20) + (15 - 10) + 5

= 5 + 5 + 10 + 5 + 5  + 5  + 5

= 5 x 6 + 10

= 40 

a) 2000

b) 0

c) 40

          234 x 13 + 234 x 87 = 234 x (13 + 87)

                               = 234 x 100

                               = 23 400

tính bang cách thuận tiện: 735-48-35

234 x 13 + 234 x 87

=234 x (13+87)

=234 x 100

=23400

`234 xx 1257 - 234 xx 257`

`= 234 xx (1257 -257)`

`= 234 xx 1000`

`= 234000`

`312 xx 415 + 312 xx 574 + 312`

`=312 xx 415 + 312 xx 574 + 312xx1`

`=312 xx(415 + 574+1)`

`= 312 xx 1000`

`= 312000`

Lời giải:
1. Bạn coi lại đề

2. $=234\times (1257-257)=234\times 1000=234000$

3. $=175\times (1274-273-1)=175\times 1000=175000$

4. $=(4\times 25)\times (125\times 8)=100\times 1000=100000$

1. ...............................

2. $=234\times (1257-257)=234\times 1000=234000$

3. $=175\times (1274-273-1)=175\times 1000=175000$

4. $=(4\times 25)\times (125\times 8)=100\times 1000=100000$

b. 2 x 8 x 50 x 25 x 125 = (2 × 50) × (8 × 125) × 25

= 100 × 1000 × 25

= 100000 × 25

= 2500000

= ( 2x50) x ( 8x125) x 25

= 100 x 1000 x 25

100000 x 25

= 2500000

b. 2 x 8 x 50 x 25 x 125 = (2 × 50) × (8 × 125) × 25

= 100 × 1000 × 25

= 100000 × 25

= 2500000

16*234+8*776*2=16*234+(8*2)*776=16*234+16*776=16*(234+776)=16*1000=16000

16 x 234 + 8 x 776 x 2

= ( 16 x 234 ) + 8 x ( 778 x 2 )

= 3744 + 8 x 1556

= 3752 x 1556

= 5838112

16*234+8*776*2=16*234+16*776

                       =16*(234+776)

                       =16*1010   

                       =16160