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a) \(\dfrac{1}{2}:y\times\dfrac{3}{5}=\dfrac{4}{3}+\dfrac{3}{4}\)
\(\dfrac{1}{2}:y\times\dfrac{3}{5}=\dfrac{25}{12}\)
\(\dfrac{1}{2}:y=\dfrac{25}{12}:\dfrac{3}{5}\)
\(\dfrac{1}{2}:y=\dfrac{125}{36}\)
\(y=\dfrac{1}{2}:\dfrac{125}{36}\)
\(y=\dfrac{18}{125}\)
b) \(\dfrac{4}{3}-\dfrac{1}{2}\times y=1\)
\(\dfrac{1}{2}\times y=\dfrac{4}{3}-1\)
\(\dfrac{1}{2}\times y=\dfrac{1}{3}\)
\(y=\dfrac{1}{3}:\dfrac{1}{2}\)
\(y=\dfrac{2}{3}\)
c) \(\dfrac{1}{4}+y:\dfrac{1}{3}=\dfrac{5}{6}\)
\(y:\dfrac{1}{3}=\dfrac{5}{6}-\dfrac{1}{4}\)
\(y:\dfrac{1}{3}=\dfrac{7}{12}\)
\(y=\dfrac{7}{12}\cdot\dfrac{1}{3}\)
\(y=\dfrac{7}{36}\)
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Bài 1:
a.
$\frac{2}{3}\times \frac{x}{y}=\frac{8}{15}$
$\frac{x}{y}=\frac{8}{15}: \frac{2}{3}=\frac{4}{5}$
b.
$\frac{x}{y}: \frac{3}{4}=\frac{2}{5}$
$\frac{x}{y}=\frac{3}{4}\times \frac{2}{5}=\frac{3}{10}$
c.
$\frac{3}{5}: \frac{x}{y}=\frac{4}{7}$
$\frac{x}{y}=\frac{3}{5}: \frac{4}{7}=\frac{21}{20}$
Bài 2:
Chiều dài hình chữ nhật là:
$\frac{3}{5}: \frac{3}{4}=\frac{4}{5}$ (m)
Chu vi hình chữ nhật:
$2\times (\frac{3}{4}+\frac{4}{5})=\frac{31}{10}$ (m)
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\(a,y+\dfrac{2}{3}=\dfrac{5}{2}\)
\(y=\dfrac{5}{2}-\dfrac{2}{3}\)
\(y=\dfrac{15}{6}-\dfrac{4}{6}\)
\(y=\dfrac{11}{6}\)
\(b,3\dfrac{4}{5}-y=\dfrac{18}{5}\)
\(y=3\dfrac{4}{5}-\dfrac{18}{5}\)
\(y=\dfrac{19}{5}-\dfrac{18}{5}\)
\(y=\dfrac{1}{5}\)
\(c,y-4\dfrac{5}{6}=2\dfrac{1}{6}+\dfrac{5}{6}\)
\(y-\dfrac{29}{6}=\dfrac{13}{6}+\dfrac{5}{6}\)
\(y-\dfrac{29}{6}=\dfrac{18}{6}\)
\(y=\dfrac{18}{6}+\dfrac{29}{6}\)
\(y=\dfrac{47}{6}\)
![](https://rs.olm.vn/images/avt/0.png?1311)
![](https://rs.olm.vn/images/avt/0.png?1311)
Bài 4:
\(\dfrac{3}{4}+y:\dfrac{2}{5}=\dfrac{37}{16}\)
\(\Rightarrow y:\dfrac{2}{5}=\dfrac{37}{16}-\dfrac{3}{4}\)
\(\Rightarrow y:\dfrac{2}{5}=\dfrac{25}{16}\)
\(\Rightarrow y=\dfrac{2}{5}\cdot\dfrac{25}{16}\)
\(\Rightarrow y=\dfrac{5}{8}\)
________________
\(456+y:87=23987\)
\(\Rightarrow y:87=23987-456\)
\(\Rightarrow y:87=23531\)
\(\Rightarrow y=23531\cdot87\)
\(\Rightarrow y=2047197\)
a)\(\dfrac{4}{5}\times\dfrac{5}{8}:\dfrac{4}{5}\)
\(=\left(\dfrac{4}{5}:\dfrac{4}{5}\right)\times\dfrac{5}{8}\)
\(=1\times\dfrac{5}{8}=\dfrac{5}{8}\)
b)\(\dfrac{5}{6}+\left(\dfrac{1}{2}:\dfrac{3}{2}+\dfrac{4}{5}\right)\)
\(=\dfrac{5}{6}+\left(\dfrac{1}{3}+\dfrac{4}{5}\right)\)
\(=\dfrac{5}{6}+\dfrac{17}{15}\)
\(=\dfrac{59}{30}\)
Bài 2:
a) \(\dfrac{3}{4}+y:\dfrac{2}{5}=\dfrac{37}{16}\)
\(y:\dfrac{2}{5}=\dfrac{37}{16}-\dfrac{3}{4}\)
\(y:\dfrac{2}{5}=\dfrac{25}{16}\)
\(y=\dfrac{25}{16}\times\dfrac{2}{5}\)
\(y=\dfrac{5}{8}\)
b)\(456+y:87=23987\)
\(y:87=23987-456\)
\(y:87=23531\)
\(y=23531\times87\)
\(y=2047197\)