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\(\dfrac{5}{22}+\dfrac{4}{11}=\dfrac{5}{22}+\dfrac{8}{22}=\dfrac{13}{22}\)
\(\dfrac{5}{22}+\dfrac{4}{11}=\dfrac{5}{22}+\dfrac{4\times2}{11\times2}=\dfrac{5}{22}+\dfrac{8}{22}=\dfrac{5+8}{22}=\dfrac{13}{22}\)
![](https://rs.olm.vn/images/avt/0.png?1311)
c)\(=\dfrac{5\times17\times2}{17\times5\times2}=1\)
\(=\dfrac{99}{33}=3\)
d)\(=4\times\dfrac{16}{3}=\dfrac{64}{3}\)
còn lại ko nhìn đc
![](https://rs.olm.vn/images/avt/0.png?1311)
Đổi : \(30km=3000000cm\)
Độ dài thu nhỏ :
\(3000000:10000=300\left(cm\right)\)
Đổi : \(20m=20000mm\)
Độ dài thu nhỏ :
\(20000:5000=4000\left(mm\right)\)
Đổi \(10m=1000m\)
Độ dài thu nhỏ :
\(1000:200=500\left(cm\right)\)
Đổi : \(2km=20000dm\)
Độ dài thu nhỏ :
\(20000:20000=1\left(dm\right)\)
![](https://rs.olm.vn/images/avt/0.png?1311)
\(\dfrac{12}{5}+3=\dfrac{12}{5}+\dfrac{15}{5}=\dfrac{12+15}{5}=\dfrac{27}{5}\)
![](https://rs.olm.vn/images/avt/0.png?1311)
a.\(y:\dfrac{4}{5}=\dfrac{11}{8}\)
\(y=\dfrac{11}{8}\times\dfrac{4}{5}\)
\(y=\dfrac{11}{10}\)
b.\(\dfrac{11}{3}-y=\dfrac{1}{9}\)
\(y=\dfrac{11}{3}-\dfrac{1}{9}\)
\(y=\dfrac{32}{9}\)
c.\(\dfrac{1}{7}\times x=\dfrac{8}{5}\)
\(x=\dfrac{8}{5}:\dfrac{1}{7}\)
\(x=\dfrac{56}{5}\)
![](https://rs.olm.vn/images/avt/0.png?1311)
\(\dfrac{2}{7}+\dfrac{13}{14}=\dfrac{4}{14}+\dfrac{13}{14}=\dfrac{4+13}{14}=\dfrac{17}{14}\)
\(\dfrac{2}{7}+\dfrac{13}{14}=\dfrac{2\times2}{7\times2}+\dfrac{13}{14}=\dfrac{4}{14}+\dfrac{13}{14}=\dfrac{4+13}{14}=\dfrac{17}{14}\)
![](https://rs.olm.vn/images/avt/0.png?1311)
\(\dfrac{8}{3}-\dfrac{5}{7}=\dfrac{8\times7}{3\times7}-\dfrac{5\times3}{7\times3}=\dfrac{56}{21}-\dfrac{15}{21}=\dfrac{56-15}{21}=\dfrac{41}{21}\)
\(\dfrac{8}{3}-\dfrac{5}{7}=\dfrac{56}{21}-\dfrac{15}{21}=\dfrac{56-15}{21}=\dfrac{41}{21}\)
\(\dfrac{5}{17}\times\dfrac{34}{25}=\dfrac{5\times17\times2}{17\times5\times5}=\dfrac{2}{5}\)
\(\dfrac{5}{17}\times\dfrac{34}{25}=\dfrac{5\times34}{17\times25}=\dfrac{170}{425}=\dfrac{2}{5}\)