17x42+67x58-50x28

= (42+58) x (67-17)-(50x28)

= 100 x 50 - 1400

= 5000 - 1400

= 3600

17*42+67*58-50*28=

  714+3886-1400=

   4600-1400=

     3200

nhớ giải bằng cách hợp lí ra nhé

Các bạn nhớ ghi cách làm ra nhé!

\(\text{a.61 x 23 + 39 x 22}\)

\(=61.22+1+39.22\)

\(=22.\left(61+39\right)+1\)

\(=22.100+1\)

\(=2200+1\)

\(=2201\)

mình chỉ làm được 1 câu thôi

hok tốt

61*23+39*22

=(61+39)*22+61

=100*22+61

=2200+61

=2261

61 x 23 + 39 x 22 = 61 x ( 22 + 1 ) + 39 x 22 = 61 x 22 + 61 + 39 x 22 = 22 x ( 61 + 39 ) + 61 = 22 x 100 + 61 = 2 200 +61 = 2 261

Lời giải:
$2\times A=\frac{2}{1\times 3}+\frac{2}{3\times 5}+\frac{2}{5\times 7}+...+\frac{2}{19\times 21}$
$2\times A=\frac{3-1}{1\times 3}+\frac{5-3}{3\times 5}+\frac{7-5}{5\times 7}+...+\frac{21-19}{19\times 21}$

$=1-\frac{1}{3}+\frac{1}{3}-\frac{1}{5}+....+\frac{1}{19}-\frac{1}{21}$

$=1-\frac{1}{21}=\frac{20}{21}$

$\Rightarrow A=\frac{20}{21}: 2= \frac{10}{21}$

\(\frac{13}{50}+74\%+\frac{41}{100}+0,59\)

\(=\frac{26}{100}+\frac{74}{100}+\frac{41}{100}+\frac{59}{100}\)

\(=\frac{\left(26+74\right)+\left(41+59\right)}{100}\)

\(=2\)

Ta có:

13/50+ 74% +41/100 +0,59

=26%+ 74%+ 41% +59%

=200%= 2

BẰNG 2

(7x6):(7x6)=1

42:42=1

(7:7)x(6:6)=1

`@` `\text {Ans}`

`\downarrow`

`2023 \times 14 + 2023 \times 83+97`

`= 2023 \times (14+83) + 97`

`= 2023 \times 97 + 97`

`= 196231 +97`

`= 196328`

`78 \times 31+78 \times 24+78 \times 17+78 \times 22 \times 72`

`= 78 \times (31+24+17+22 \times 72)`

`= 78 \times (31+24+17+1584)`

`= 78 \times 1656`

`= 129168`

`371 \times 69+371 \times 14+629 \times 83`

`= 371 \times (69+14) + 629 \times 83`

`= 371 \times 83 + 629 \times 83`

`= 83 \times (371+629)`

`= 83 \times 1000`

`= 83000`

`91 \times 51+49 \times 163-49 \times 72`

`= 91 \times 51 + 49 \times (163-72)`

`= 91 \times 51+49 \times 91`

`= 91 \times (51+49)`

`= 91 \times 100`

`= 9100`

`3 \times 12 \times 17 + 4 \times 9 \times 81 + 2 \times 6 \times 6`

`= 9 \times 4 \times 17 + 4 \times 9 \times 81 + 4 \times 9 \times 2`

`= 9 \times 4 \times (17+81+2)`

`= 36 \times 100` 

`= 3600`

`42 \times 17 + 58 \times 83 \times 42 \times 83 + 42 \times 83 + 17`

`= 17 \times (42+58) + 42 \times 83 \times (58 \times 83 +1)`

`= 17 \times 100 + 3486 \times 4815`

`= 1700 + 16785090`

`= 16786790`

13/19 x 5/17 + 12/17 x 13/19

= 13/19 x (5/17 + 12/17)

= 13/19 x 1

= 13/19