4/7 - 12/21

15/8 - 45/24

8/9 - 16/18

20/28 - 5/7

\(\dfrac{4}{7}=\dfrac{12}{21};\dfrac{15}{8}=\dfrac{45}{24};\dfrac{8}{9}=\dfrac{16}{18};\dfrac{5}{7}=\dfrac{20}{28}\)

4/7 - 12/21

15/8 - 45/24 

8/9 - 16/18

20/28 - 5/7 

\(\dfrac{14}{21}=\dfrac{2}{3}\\ \dfrac{12}{15}=\dfrac{8}{10}\\ \dfrac{5}{7}=\dfrac{20}{28}\\ \dfrac{18}{33}=\dfrac{6}{11}\)

a,       5/4 , 14/21 , 12/15 , 5/7 , 18/33                                                                         

  b,       20/28 ,  15/12 , 6/11 , 2/3 , 8/10   

14/21=2/3

20/28=5/7

18/33=6/11

\(\dfrac{5}{6}=\dfrac{15}{18}\)

\(\dfrac{9}{11}=\dfrac{27}{33}\)

\(\dfrac{5}{8}=\dfrac{25}{40}\)

\(\dfrac{12}{16}=\dfrac{36}{48}\)

\(\dfrac{8}{12}=\dfrac{40}{60}\)

5/6= 27/33

12/16= 36/48

8/12= 40/60

25/40= 5/8

15/18= 5/6

B

B

B

Chọn C

\(\frac{2}{5}\Leftrightarrow\frac{14}{35}\)

\(\frac{18}{48}\Leftrightarrow\frac{3}{8}\)

\(\frac{4}{7}\Leftrightarrow\frac{20}{35}\)

`1/2= 2/4=4/8`

`36/96=12/32=3/8`

`12/18=6/8=3/4`

\(\dfrac{12}{28}\)

\(\dfrac{12}{28}\)

6/14;12/28