\(a,\dfrac{2}{13}\times\dfrac{22}{5}\times\dfrac{13}{2}\\ =\left(\dfrac{2}{13}\times\dfrac{13}{2}\right)\times\dfrac{22}{5}\\ =1\times\dfrac{22}{5}=\dfrac{22}{5}\\ b,\dfrac{3}{5}\times\dfrac{6}{7}+\dfrac{6}{7}\times\dfrac{3}{5}\\ =\dfrac{3}{5}\times\left(\dfrac{6}{7}+\dfrac{6}{7}\right)\\ =\dfrac{3}{5}\times\dfrac{12}{7}=\dfrac{36}{35}\)

\(a,=\left(\dfrac{2}{13}\times\dfrac{13}{2}\right)\times\dfrac{22}{5}=\dfrac{22}{5}\\ b,=\dfrac{3}{5}\times\left(\dfrac{6}{7}+\dfrac{6}{7}\right)\\ =\dfrac{3}{5}\times\dfrac{12}{7}\\ =\dfrac{36}{35}\)

a) 683\(\times\) 35=23906

    1954\(\times\) 425=830450

    2438\(\times\) 306=746028

b) \(\dfrac{7}{9}\times\dfrac{3}{35}=\dfrac{7\times3}{9\times35}=\dfrac{1}{15}\) 

\(\dfrac{9}{22}\times55=\dfrac{9\times55}{22}=\dfrac{45}{2}\) 

\(\dfrac{11}{17}:\dfrac{33}{34}=\dfrac{11}{17}\times\dfrac{34}{33}=\dfrac{11\times34}{17\times33}=\dfrac{2}{3}\) 

c) 36,66:7,8=4,7

     15,7:6,28=2,5

      27,63:0,45=61,4

d) 16 giờ 15 phút:5=3 giờ 15 phút

    14 phút 36 giây:12=1 phút 13 giây

a) \(\dfrac{3}{5}\times\dfrac{17}{21}+\dfrac{2}{5}\times\dfrac{17}{21}\)

\(=\dfrac{17}{21}\times\left(\dfrac{3}{5}+\dfrac{2}{5}\right)\)

\(=\dfrac{17}{21}\times1\)

\(=\dfrac{17}{21}\)

b) \(\dfrac{11}{19}\times\dfrac{2}{7}+\dfrac{5}{7}\times\dfrac{11}{19}\)

\(=\dfrac{11}{19}\times\left(\dfrac{2}{7}+\dfrac{5}{7}\right)\)

\(=\dfrac{11}{19}\times1\)

\(=\dfrac{11}{19}\)

a: =17/21(3/5+2/5)

=17/21*5/5

=17/21

b: =11/19(2/7+5/7)

=11/19*1

=11/19

a) \(\dfrac{3}{22}\times\dfrac{3}{11}\times22\)

\(=\dfrac{3}{22}\times\dfrac{3}{11}\times\dfrac{22}{1}\)

\(=\dfrac{3\times3\times22}{22\times11\times1}\)

\(=\dfrac{9}{11}\)

b) \(\left(\dfrac{1}{3}+\dfrac{1}{6}\right)\times\dfrac{2}{5}\)

\(=\left(\dfrac{2}{6}+\dfrac{1}{6}\right)\times\dfrac{2}{5}\)

\(=\dfrac{3}{6}\times\dfrac{2}{5}\)

\(=\dfrac{1}{2}\times\dfrac{2}{5}\)

\(=\dfrac{2}{10}\)

\(=\dfrac{1}{5}\)

a: =3/22*22*3/11

=3*3/11

=9/11

b: =(2/6+1/6)*2/5

=1/2*2/5

=1/5

C)

`7/19xx5/8xx (-19)/7`

`=7/19xx (-19/7)xx5/8`

`= -1xx5/8`

`=-5/8`

D)

`3/7xx9/11+3/7xx2/11`

`=3/7xx(9/11+2/11)`

`=3/7xx11/11`

`=3/7xx1`

`=3/7`

a)

\(\dfrac{3}{5}\times\dfrac{7}{11}\times\dfrac{5}{3}\times11\\ =\left(\dfrac{3}{5}\times\dfrac{5}{3}\right)\times\left(\dfrac{7}{11}\times11\right)\\ =\dfrac{3\times5}{5\times3}\times\dfrac{7\times11}{11}\\ =1\times7\\ =7\)

b)

\(\dfrac{3}{8}\times\dfrac{2}{7}+\dfrac{5}{7}\times\dfrac{3}{8}\\ =\dfrac{3}{8}\times\left(\dfrac{2}{7}+\dfrac{5}{7}\right)\\ =\dfrac{3}{8}\times\dfrac{7}{7}\\ =\dfrac{3}{8}\times1=\dfrac{3}{8}\)

1

a) \(\dfrac{2}{5}\times?=\dfrac{3}{10}\)

\(?=\dfrac{3}{10}:\dfrac{2}{5}=\dfrac{3}{4}\)

b) \(\dfrac{1}{8}:?=\dfrac{1}{5}\)

\(?=\dfrac{1}{8}:\dfrac{1}{5}=\dfrac{5}{8}\)

a: Phân số cần tìm là: \(\dfrac{3}{10}:\dfrac{2}{5}=\dfrac{3}{10}\cdot\dfrac{5}{2}=\dfrac{15}{20}=\dfrac{3}{4}\)

b: Phân số cần tìm là \(\dfrac{1}{8}:\dfrac{1}{5}=\dfrac{5}{8}\)

a) \(\dfrac{3}{5}+\dfrac{7}{25}=\dfrac{15}{25}+\dfrac{7}{25}=\dfrac{15+7}{25}=\dfrac{22}{25}\)

b) \(\dfrac{8}{11}-\dfrac{19}{33}=\dfrac{24}{33}-\dfrac{19}{33}=\dfrac{24-19}{33}=\dfrac{5}{33}\)

c) \(\dfrac{16}{21}\times\dfrac{3}{5}=\dfrac{16\times3}{21\times5}=\dfrac{48}{105}=\dfrac{16}{35}\)

d) \(\dfrac{14}{41}\div\dfrac{7}{9}=\dfrac{14}{41}\times\dfrac{9}{7}=\dfrac{14\times9}{41\times7}=\dfrac{126}{287}=\dfrac{18}{41}\)

`# \text {DNamNgV}`

`16/21 + 6/7`

`= 16/21 + 18/21`

`= 34/21`

__

`15/22 \times 11/35`

`= (15 \times 11)/(22 \times 35)`

`= (5 \times 3 \times 11)/(2 \times 11 \times 5 \times 7)`

`= (3 \times 1)/(2 \times 7)`

`= 3/14`

___

`8/11 \div 5/22`

`= 8/11 \times 22/5`

`= (8 \times 22)/(11 \times 5)`

`= (8 \times 11 \times 2)/(11 \times 5)`

`= (8 \times 2)/5`

`= 16/5`

___

`9/13 \div 27/39`

`= 9/13 \times 39/27`

`= 9/13 \times 13/9`

`= 1`