36 bạn

16 bạn

`3/7 : 2`

`= 3/7 xx 1/2`

`= 3/14`

CÚT CHÓ

`4/5xx13`

`=4/5xx13/1`

`=52/5`

\(\dfrac{3}{7}-\dfrac{1}{14}=\dfrac{6}{14}-\dfrac{1}{14}=\dfrac{5}{14}\)

3/7 - 1/14 = 6/14 - 1/14 = 5/14

\(\dfrac{5}{12}+\dfrac{1}{6}=\dfrac{5}{12}+\dfrac{2}{12}=\dfrac{7}{12}\)

5/12 + 1/6 = 5/12 + 2/12 = 7/12

`5/6:3/4`

`=5/6xx4/3`

`=20/18=10/9`

5/6 : 3/4 = 5/6 x 4/3 = 20/18 = 10/9

`5/6-3/4`

`=20/24-18/24`

`=2/24=1/12`

     \(\dfrac{5}{6}\) - \(\dfrac{3}{4}\)

=   \(\dfrac{10}{12}\) - \(\dfrac{9}{12}\)

= \(\dfrac{1}{12}\)

theo đề bài ta có

\(\dfrac{3}{5}< \dfrac{x}{5}< \dfrac{4}{5}\\ =>\dfrac{15}{25}< \dfrac{x}{25}< \dfrac{20}{25}\)

=> 4 phân số đó là \(\dfrac{16}{25};\dfrac{17}{25};\dfrac{18}{25};\dfrac{19}{25}\)

\(\dfrac{3}{5}\) = \(\dfrac{3\times5}{5\times5}\) = \(\dfrac{15}{25}\);

\(\dfrac{4}{5}\) = \(\dfrac{4\times5}{5\times5}\) = \(\dfrac{20}{25}\)

Vậy bốn phân số nằm giữa \(\dfrac{3}{5}\)và \(\dfrac{4}{5}\) là bốn phân số nằm giữa \(\dfrac{15}{25}\) và\(\dfrac{20}{25}\), đó lần lượt là các phân số sau:

\(\dfrac{16}{25}\); \(\dfrac{17}{25}\); \(\dfrac{18}{25}\); \(\dfrac{19}{25}\)

\(\dfrac{23}{5}\) + \(\dfrac{11}{3}\) 

= \(\dfrac{69}{15}\) + \(\dfrac{55}{15}\)

= \(\dfrac{124}{15}\)

    \(\dfrac{2}{3}\) + \(\dfrac{4}{5}\)

=  \(\dfrac{10}{15}\) + \(\dfrac{12}{15}\)

= \(\dfrac{22}{15}\)