Phép chia phân số

a: \(\dfrac{2}{5}+\dfrac{7}{8}=\dfrac{2\cdot8+7\cdot5}{40}=\dfrac{16+35}{40}=\dfrac{51}{40}\)

b: \(\dfrac{9}{14}\cdot\dfrac{28}{18}=\dfrac{9}{18}\cdot\dfrac{28}{14}=\dfrac{2}{2}=1\)

c: \(\dfrac{9}{17}-\dfrac{2}{51}=\dfrac{9\cdot3-2}{51}=\dfrac{25}{51}\)

d: \(\dfrac{4}{5}:\dfrac{8}{5}=\dfrac{4}{5}\cdot\dfrac{5}{8}=\dfrac{4}{8}=\dfrac{1}{2}\)

Sửa đề: ngày 2 đọc 4/8 cuốn sách

Sau ngày 1 còn 1-1/3=2/3(cuốn)

Sau ngày 2 còn 2/3*1/2=1/3(cuốn)

Cuốn sách có độ dài là: 36:1/3=108(cuốn)

7/8 : x = 1/2

x = 7/8 : 1/2

x = 7/8 × 2

x = 7/4

\(\dfrac{7}{8}:x=\dfrac{1}{2}\)

\(\Leftrightarrow x=\dfrac{7}{8}:\dfrac{1}{2}\)

\(\Leftrightarrow x=\dfrac{7}{8}\times\dfrac{2}{1}\)

\(\Leftrightarrow x=\dfrac{14}{8}=\dfrac{7}{4}\)

`9/3` : `3/4`

= `9/3` \(\times\) `4/3`

= `36/9' = 4.

`9/3:3/4=9/3xx4/3=4`

\(\dfrac{9}{3}:\dfrac{3}{4}=\dfrac{9}{3}\times\dfrac{4}{3}=\dfrac{36}{9}=4\)

`24/36 - 3`

`=2/3-3`

`=2/3-9/3`

`= -7/3`

`24/36-3`

`=24/36-108/36`

`=-84/36=-7/3`

bằng 8,12 nhé

\(2:\dfrac{2}{3}-\dfrac{1}{7}=3-\dfrac{1}{7}=\dfrac{20}{7}\)

2 : \(\dfrac{2}{3}\) - \(\dfrac{1}{7}\) = 2 x \(\dfrac{2}{3}\) - \(\dfrac{1}{7}\) = 3 - \(\dfrac{1}{7}\)  = \(\dfrac{20}{7}\)

2 : 2/3 - 1/7

= 2 x 3/2

= 6/2

= 3 -1/7

= 20/7

ko đăng lại

`8 / 3 : 1 / 2 + 1 = 8 / 3 xx 2 + 1 = 16 / 3 + 3 / 3 = 19 / 3`

8/3:1/2+1

= 16/3+1

=19/3

= 8/3 x 2 + 1

= 16/3 + 1

= 19/3

8/3:1/2+1

= 16/3+1

= 19/3

8/3 : 1/2 +1= 8/3 x 2 + 1= 16/3 + 1= 19/3

\(\dfrac{7}{3}x\dfrac{1}{2}=\dfrac{7}{6}\)

7/6

\(\dfrac{7}{3}:2=\dfrac{7}{6}\)

* là chia ?

\(\dfrac{3}{4}:\dfrac{1}{9}\times\dfrac{5}{7}:\dfrac{1}{4}=\dfrac{3}{4}\times9\times\dfrac{5}{7}\times4=\dfrac{135}{7}\)

\(\dfrac{140}{143}\times\dfrac{5}{7}=\dfrac{100}{143}\)

Bạn viết rõ lại tí đc ko