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a: \(=\dfrac{3}{5}\cdot\dfrac{5}{4}+\dfrac{1}{2}\cdot\dfrac{2}{3}=\dfrac{3}{4}+\dfrac{1}{3}=\dfrac{9+4}{12}=\dfrac{13}{12}\)
b: \(\Leftrightarrow x\cdot\dfrac{5}{4}=\dfrac{5}{8}\)
hay x=1/2
Bài 1
1/2 x 3/4 : 4/5
= 3/8 : 4/5
= 3/8 x 5/4
= 15/32
2/3 + 1/6 - 1/2
= 4/6 + 1/6 - 3/6
= 5/6 - 3/6
= 1/3
3/5 + 4 : 2/3 - 3/2
= 3/5 + 4 x 3/2 - 3/2
= 3/5 + 6 - 3/2
= 3/5 + 30/5 - 3/2
= 33/5 - 3/2
= 66/10 - 15/10
= 28/5
Bài 2
x - 1/4 = 1/2
x = 1/2 + 1/4
x = 2/4 + 1/4
x = 3/4
2/3 + x = 1
x = 1 - 2/3
x = 3/3 - 2/3
x = 1/3
A) \(\frac{4}{5}+\frac{5}{4}-2=\frac{16}{20}+\frac{25}{20}-\frac{40}{20}\)
\(=\frac{1}{20}\)
B) \(3-\frac{2}{3}-\frac{3}{2}=\frac{18}{6}-\frac{4}{6}-\frac{9}{6}\)
\(=\frac{5}{6}\)
C) \(\frac{7}{8}-\left(\frac{1}{4}+\frac{2}{5}\right)=\frac{7}{8}-\frac{13}{20}\)
\(=\frac{35}{40}-\frac{26}{40}=\frac{9}{40}\)
D) \(\frac{9}{10}-\left(\frac{2}{5}+\frac{3}{10}\right)+\frac{7}{10}=\frac{9}{10}-\frac{7}{10}+\frac{7}{10}\)
\(=\frac{9}{10}\)
a) \(\dfrac{1}{3}+\dfrac{4}{3}\times\dfrac{1}{2}=\dfrac{1}{3}+\dfrac{4}{6}=\dfrac{1}{3}+\dfrac{2}{3}=\dfrac{3}{3}=1\)
b) \(\dfrac{3}{5}\times\dfrac{4}{7}:\dfrac{16}{21}=\dfrac{3}{5}\times\dfrac{4}{7}\times\dfrac{21}{16}=\dfrac{12}{35}\times\dfrac{21}{16}=\dfrac{252}{560}=\dfrac{9}{20}\)
a, 2 \(\times\) \(\dfrac{2}{4}\) : \(\dfrac{4}{5}\) b, \(\dfrac{7}{8}\) \(\times\) \(\dfrac{4}{5}\) : 3
= 1 : \(\dfrac{4}{5}\) = \(\dfrac{7}{10}\) : 3
= 1 \(\times\) \(\dfrac{5}{4}\) = \(\dfrac{7}{10}\) \(\times\) \(\dfrac{1}{3}\)
= \(\dfrac{5}{4}\) = \(\dfrac{7}{30}\)
\(2\times\dfrac{2}{4}:\dfrac{4}{5}\)
\(=1:\dfrac{4}{5}\)
\(=1\times\dfrac{5}{4}\)
\(=\dfrac{5}{4}\)
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\(\dfrac{7}{8}\times\dfrac{4}{5}:3\)
\(=\dfrac{7}{2}\times\dfrac{1}{5}:3\)
\(=\dfrac{7}{10}\times\dfrac{1}{3}\)
\(=\dfrac{7}{30}\)
Chúc bạn học tốt:>