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

(234x 4) x (25x4)

=936 x 100

=93600

234 x 24 - 234 x 14 + 234

= 234 x 24 - 234 x 14 + 234 x 1

= 234 x (24 - 14 + 1)

= 234 x 11

= 2574

234 x ( 24 - 14 ) =

234 x 10 = 2340

234x24-234x14+234

=234x24-234x14+234x1

=234x(24-14+1)

=234x11

=2574

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 + 177 + 16 + 23 = (234 + 16) + (177 + 23) = 250 + 200 = 450

b) 1 + 2 + 3 + 97 + 98 + 99 = (1 + 99) + (2 + 98) + (3 + 97) = 100 + 100 + 100 = 300

ko phải tính nhanh

   1,234 x 4 + 1,234 x 3 + 1,234 x 2 + 1,234

= 1,234 ( 4+3+2+1)

= 1,234 x 10

= 12,34

1,234*4+1,234*3+1,234*2+1,234

=1,234* [4+3+2+1] =1,234*10 =12,34

a) \(\left(81+19\right)+35=135\)

b) \(\left(78+22\right)+\left(65+135\right)=100+200=300\)

c) \(\left(234+17716\right)+23=17950+23=17973\)

d) \(\left(99+1\right)+85=100+85=185\)

\(a,81+35+19=\left(81+19\right)+35=100+35=135\\ b,78+65+135+22=\left(78+22\right)+\left(65+135\right)=100+200=300\\ c,234+17716+23=\left(234+17716\right)+23=17950+23=17973\\ d,85+99+1=85+\left(99+1\right)=85+100=185\)

A) 81+ 19 +35

=100+35=135

B) 78+65+135+22

=78+22+65+135

100+200=300 

mấy câu cx làm tương tự

`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`

a: =1250:25=50

b: =234(45+55)+234=23400+234=23634

c: =1000x1000=1000000