dấu . là nhân hay là phần ngăn cách ở hàng phần nghìn thế

a) \(28400:\left(100\times311-310\times100\right)\)
\(=28400:\left[\left(311-310\right)\times100\right]\)
\(=28400:100\)
\(=284\)
b) \(\dfrac{5}{11}+\dfrac{19}{15}+\dfrac{6}{11}+\dfrac{11}{16}+\dfrac{6}{15}+\dfrac{5}{16}\)
\(=\left(\dfrac{5}{11}+\dfrac{6}{11}\right)+\left(\dfrac{19}{15}+\dfrac{6}{15}\right)+\left(\dfrac{11}{16}+\dfrac{5}{16}\right)\)
\(=1+\dfrac{5}{3}+1\)
\(=\dfrac{8}{3}+1\)
\(=\dfrac{11}{3}\)

A, = 18,95 x (75 + 24 + 1) = 18,95 x 100 = 1895

c: =7,15x2+7,15x7+7,15=7,15x10=71,5

a) 12,4 x 72,53 + 27,47 x 12,4

= 12,4×(72,53+27,47)

=12,4×100

=1240

= 12,4 × (72,53 + 27,47)

= 12,4 × 100

= 124

`#040911`

`a)`

`27 \times 38 + 62 \times 27 - 27 \times 90`

`= 27 \times (38 + 62 - 90)`

`= 27 \times (100 - 90)`

`= 27 \times 10`

`= 270`

\(27\times38+62\times27-27\times90\)

\(=27\times\left(38+62-90\right)\)

\(=27\times\left(100-90\right)\)

\(=27\times10\)

\(=270\)

A) 8

b) ( 3,27 + 6,73 ) x 4,35

= 10 x 4,35

= 43,5

Tính bằng cách thuận tiện:

a, 6,4 x 1,25=8                    b, 3,27 x 4,35 + 4,35 x 6,73 = ( 3,27 + 6,73) x 4,35 = 10 x 4,35 = 43,5

264,14 : 0,25 : 4

= 264,14 : ( 0,25 x 4 )

= 264,14 : 1

= 264,14 

36,45 : 0,2 x 2 : 5

=  36,45 : ( 2 x 5 ) : 0,2

= 36,45 : 10 : 0,2 

= 3,645 : 0,2

= 18,225

a) 3 kg + 30 kg + 270 kg = 3 kg + (30 kg + 270 kg)

                                         = 3 kg + 300 kg

                                         = 303 kg

b) 320 km + 32 km + 680 km + 68 km

= (320 km + 680 km) + (32 km + 68 km)

= 1 000 km + 100 km

= 1 100 km

c) 2 500 $\ell $ + 2 900 $\ell $ + 2 100 $\ell $ + 2 500 $\ell $

= (2 500 $\ell $ + 2 500 $\ell $) + (2 900 $\ell $ + 2 100 $\ell $)

= 5 000 $\ell $ + 5 000 $\ell $

= 10 000 $\ell $

a/\(0,25\times611,7\times4\)
\(=\left(0,25\times4\right)\times611,7\)
\(=1\times611,7\)
\(=611,7\)
b/\(17,6\times3,21+3,21\times42,4+3,21\times40\)
\(=3,21\times\left(17,6+42,4+40\right)\)
\(=3,21\times100\)
\(=321\)
#kễnh