2/7 / 1/7 = 10/28 = 5/14

3/8 / 9/4 = 12/72 = 2/12

8/21 / 4/7 = 56/84 = 14/21

5/8 / 15 / 8 = 1/24 / 8 = 1/192

\(a,\frac{2}{7}:\frac{4}{5}=\frac{2}{7}\times\frac{5}{4}=\frac{10}{28}=\frac{5}{14}\)

\(b,\frac{3}{8}:\frac{9}{4}=\frac{3}{8}\times\frac{4}{9}=\frac{12}{72}=\frac{1}{6}\)

\(c,\frac{8}{21}:\frac{4}{7}=\frac{8}{21}\times\frac{7}{4}=\frac{56}{84}=\frac{2}{3}\)

\(d,\frac{5}{8}:\frac{15}{8}=\frac{5}{8}\times\frac{8}{15}=\frac{40}{120}=\frac{1}{3}\)

A,\(\frac{2}{7}:\frac{4}{5}=\frac{2}{7}\times\frac{5}{4}=\frac{10}{28}=\frac{5}{14}\)

B,\(\frac{3}{8}:\frac{9}{4}=\frac{3}{8}\times\frac{4}{9}=\frac{12}{72}=\frac{1}{6}\)

C.\(\frac{8}{21}:\frac{4}{7}=\frac{8}{21}\times\frac{7}{4}=\frac{56}{84}=\frac{2}{3}\)

D.\(\frac{5}{8}:\frac{15}{8}=\frac{5}{8}\times\frac{8}{15}=\frac{40}{120}=\frac{1}{3}\)

Đúng 100%

a, \(\frac{2}{7}:\frac{4}{5}=\)\(\frac{2}{7}x\)\(\frac{5}{4}\)\(\frac{10}{28}=\frac{5}{14}\)

b,\(\frac{3}{8}:\frac{9}{4}\)\(=\frac{3}{8}x\)\(\frac{4}{9}\)\(=\frac{12}{72}=\frac{1}{6}\)

c,\(\frac{8}{21}:\frac{4}{7}\)\(=\frac{8}{21}x\)\(\frac{7}{4}\)\(=\frac{56}{84}=\frac{2}{3}\)

d,\(\frac{5}{8}:\frac{15}{8}\)\(\frac{5}{8}x\)\(\frac{8}{15}=\frac{40}{120}=\frac{1}{3}\)

tk giup mk nha

rút gọn phân số :

4/5+21/15=4/5+7/5=11/5

8/9-25/45=8/9-5/9=3/9

tính :

5/6+2/7+15/6=5/6+15/6+2/7

=10/3+2/7=76/21

7/8-9/6.7/8=7/8-21/16=-7/16 

chúc bạn học tốt !!!

`8/56+3/21`

`=1/7+1/7`

`=2/7`

=1/7 + 1/7 =2/7

\(\dfrac{8}{56}+\dfrac{3}{21}\)
\(=\dfrac{1}{7}+\dfrac{1}{7}\)
\(=\dfrac{2}{7}\)

28/35+21/28+7/21+1/7

=4/5+3/4+1/3+1/7

=851/420

dùng máy tính là ok mà bn.

\(\frac{28}{35}+\frac{21}{28}+\frac{9}{21}+\frac{1}{7}\)

\(=(\frac{4}{5}+\frac{3}{4})+(\frac{3}{7}+\frac{1}{7})\)

\(=\frac{31}{20}+\frac{4}{7}\)

\(=2\frac{17}{140}\)

Chúc bn học tốt!!!!

a)2/3x4/7=8/21

b)8/21:2/3=8/21x3/2=24/42=4/7

c)8/21:4/7=8/21x7/4=56/85=7//12

d)4/7X2/3=8/21

a)\(\frac{2}{3}\cdot\frac{4}{7}=\frac{8}{21}\)

b)\(\frac{8}{21}:\frac{2}{3}=\frac{8}{21}\cdot\frac{3}{2}=\frac{4}{7}\)

c)\(\frac{8}{21}:\frac{4}{7}=\frac{8}{21}\cdot\frac{7}{4}=\frac{2}{3}\)

d)\(\frac{4}{7}\cdot\frac{2}{3}=\frac{8}{21}\)

2/3 x 4/7 = \(\frac{2.4}{3.7}=\frac{8}{21}\)

\(\frac{8}{21}:\frac{4}{7}=\frac{8\times7}{21\times4}=\frac{56}{84}=\frac{2}{3}\)

\(\frac{8}{21}:\frac{2}{3}=\frac{8\times3}{21\times2}=\frac{24}{42}=\frac{4}{7}\)

\(\frac{4}{7}\times\frac{2}{3}=\frac{4\times2}{7\times3}=\frac{8}{21}\)

8/15 + 2/3 = 18/15

Rút gọn kết quả thành 6/5

3/7 + 4/8 = 52/56

Rút gọn kết quả thành 13/14

8/15+2/3=8/15+10/15=18/15=6/5

3/7+4/8=24/56+28/56=52/56=13/14

13/14

a)8/18=4/9

4/9+5/4=16/36+45/36=61/36

b)8/24=1/3

12/28=3/7

1/3+3/7=7/21+9/21=16/21

8/7+10/21=24/21+10/21=34/21

a)=8/18+5/4=4/9+5/4=61/36

b)=8/24+12/28=1/3+3/7=16/21

8/7+10/21=34/21

a=61/36;b=16/21                               

=34/21

8/15+2/3=18/15

3/7+4/8=52/56=13/14

duyet nha dung 1000000000%

a) \(\dfrac{4}{24}+\dfrac{7}{6}=\dfrac{4}{24}+\dfrac{28}{24}=\dfrac{4+28}{24}=\dfrac{32}{24}=\dfrac{4}{3}\)

b) \(\dfrac{10}{15}-\dfrac{1}{3}=\dfrac{10}{15}-\dfrac{5}{15}=\dfrac{10-5}{15}=\dfrac{5}{15}=\dfrac{1}{3}\)

c) \(\dfrac{21}{28}-\dfrac{1}{4}=\dfrac{21}{28}-\dfrac{7}{28}=\dfrac{21-7}{28}=\dfrac{14}{28}=\dfrac{1}{2}\)

d) \(\dfrac{35}{40}+\dfrac{5}{8}=\dfrac{35}{40}+\dfrac{25}{40}=\dfrac{35+25}{40}=\dfrac{60}{40}=\dfrac{3}{2}\)

\(a)\dfrac{4}{24}=\dfrac{1}{6} \\ \dfrac{1}{6}+\dfrac{7}{6}\\ =\dfrac{8}{6}=\dfrac{4}{3}\\ b)\dfrac{10}{15}=\dfrac{2}{3}-\dfrac{1}{3}\\ =\dfrac{1}{3}\\ c)\dfrac{21}{28}=\dfrac{3}{4}\\ \dfrac{3}{4}-\dfrac{1}{4}\\ =\dfrac{2}{4}=\dfrac{1}{2}\\ d)\dfrac{35}{40}=\dfrac{7}{8}\\ \dfrac{7}{8}+\dfrac{5}{8}\\ =\dfrac{12}{8}=\dfrac{3}{2}\)