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a) \(\dfrac{2}{3}+\dfrac{4}{9}=\dfrac{6}{9}+\dfrac{4}{9}+\dfrac{6+3}{9}=\dfrac{10}{9}\)
b)\(\dfrac{1}{10}+\dfrac{2}{5}=\dfrac{1}{10}+\dfrac{4}{10}=\dfrac{1+4}{10}=\dfrac{5}{10}=\dfrac{1}{2}\)
c) \(\dfrac{7}{22}-\dfrac{3}{11}=\dfrac{7}{22}-\dfrac{6}{22}=\dfrac{7-6}{22}=\dfrac{1}{22}\)
d) \(\dfrac{5}{6}-\dfrac{5}{12}=\dfrac{10}{12}-\dfrac{5}{12}=\dfrac{10-5}{12}=\dfrac{5}{12}\)
b) 
d) 
a) \(\dfrac{4}{24}+\dfrac{7}{6}=\dfrac{4}{24}+\dfrac{28}{24}=\dfrac{4+28}{24}=\dfrac{32}{24}=\dfrac{4}{3}\)
b) \(\dfrac{10}{15}-\dfrac{1}{3}=\dfrac{10}{15}-\dfrac{5}{15}=\dfrac{10-5}{15}=\dfrac{5}{15}=\dfrac{1}{3}\)
c) \(\dfrac{21}{28}-\dfrac{1}{4}=\dfrac{21}{28}-\dfrac{7}{28}=\dfrac{21-7}{28}=\dfrac{14}{28}=\dfrac{1}{2}\)
d) \(\dfrac{35}{40}+\dfrac{5}{8}=\dfrac{35}{40}+\dfrac{25}{40}=\dfrac{35+25}{40}=\dfrac{60}{40}=\dfrac{3}{2}\)
\(a)\dfrac{4}{24}=\dfrac{1}{6} \\ \dfrac{1}{6}+\dfrac{7}{6}\\ =\dfrac{8}{6}=\dfrac{4}{3}\\ b)\dfrac{10}{15}=\dfrac{2}{3}-\dfrac{1}{3}\\ =\dfrac{1}{3}\\ c)\dfrac{21}{28}=\dfrac{3}{4}\\ \dfrac{3}{4}-\dfrac{1}{4}\\ =\dfrac{2}{4}=\dfrac{1}{2}\\ d)\dfrac{35}{40}=\dfrac{7}{8}\\ \dfrac{7}{8}+\dfrac{5}{8}\\ =\dfrac{12}{8}=\dfrac{3}{2}\)
a) \(\dfrac{2}{3}-\dfrac{2}{6}=\dfrac{4}{6}-\dfrac{2}{6}=\dfrac{4-2}{6}=\dfrac{2}{6}=\dfrac{1}{3}\)
b) \(\dfrac{5}{6}-\dfrac{3}{18}=\dfrac{10}{18}-\dfrac{3}{18}=\dfrac{10-3}{18}=\dfrac{7}{18}\)
c) \(\dfrac{8}{14}-\dfrac{2}{7}=\dfrac{8}{14}-\dfrac{4}{14}=\dfrac{8-4}{14}=\dfrac{4}{14}=\dfrac{2}{7}\)
d) \(\dfrac{12}{20}-\dfrac{2}{5}=\dfrac{12}{20}-\dfrac{8}{20}=\dfrac{12-8}{20}=\dfrac{4}{20}=\dfrac{1}{5}\)
a) \(\dfrac{3}{5}:\dfrac{3}{4}=\dfrac{3}{5}\cdot\dfrac{4}{3}=\dfrac{4}{5}\)
b) \(\dfrac{2}{5}:\dfrac{3}{10}=\dfrac{2}{5}\cdot\dfrac{10}{3}=\dfrac{4}{3}\)
c) \(\dfrac{1}{8}:\dfrac{1}{6}=\dfrac{1}{8}\cdot6=\dfrac{6}{8}=\dfrac{3}{4}\)
a: \(=\dfrac{3}{5}\cdot\dfrac{4}{3}=\dfrac{12}{15}=\dfrac{4}{5}\)
b: \(=\dfrac{2}{5}\cdot\dfrac{10}{3}=\dfrac{20}{15}=\dfrac{4}{3}\)
c: \(=\dfrac{1}{8}\cdot6=\dfrac{6}{8}=\dfrac{3}{4}\)
a) \(\dfrac{4}{7}\times\dfrac{3}{5}=\dfrac{4\times3}{7\times5}=\dfrac{12}{35}\)
b) \(\dfrac{1}{3}\times\dfrac{9}{10}=\dfrac{1\times9}{3\times10}=\dfrac{9}{30}=\dfrac{3}{10}\)
c) \(\dfrac{1}{6}\times\dfrac{1}{4}=\dfrac{1}{4\times6}=\dfrac{1}{24}\)
a)
\(\dfrac{7}{24}+\dfrac{11}{6}\\ =\dfrac{7}{24}+\dfrac{11\times4}{6\times4}\\ =\dfrac{7}{24}+\dfrac{44}{24}\\ =\dfrac{7+44}{24}\\ =\dfrac{51}{24}\\=\dfrac{17}{8}\)
b)
\(3+\dfrac{5}{8}\\ =\dfrac{3\times8}{8}+\dfrac{5}{8}\\ =\dfrac{24}{8}+\dfrac{5}{8}\\ =\dfrac{29}{8}\)
c)
\(\dfrac{19}{28}-\dfrac{3}{7}\\ =\dfrac{19}{28}-\dfrac{3\times4}{7\times4}\\ =\dfrac{19}{28}-\dfrac{12}{28}\\ =\dfrac{7}{28}=\dfrac{1}{4}\)
d)
\(\dfrac{53}{21}-1\\ =\dfrac{53}{21}-\dfrac{21}{21}\\ =\dfrac{53-21}{21}\\ =\dfrac{32}{21}\)
a) \(\dfrac{7}{24}+\dfrac{11}{6}=\dfrac{7}{24}+\dfrac{44}{24}=\dfrac{7+44}{24}=\dfrac{51}{24}\)
b) \(3+\dfrac{5}{8}=\dfrac{24}{8}+\dfrac{5}{8}=\dfrac{24+5}{8}=\dfrac{29}{8}\)
c) \(\dfrac{19}{28}-\dfrac{3}{7}=\dfrac{19}{28}-\dfrac{12}{28}=\dfrac{19-12}{28}=\dfrac{7}{28}=\dfrac{1}{4}\)
d) \(\dfrac{53}{21}-1=\dfrac{53}{21}-\dfrac{21}{21}=\dfrac{53-21}{21}=\dfrac{32}{21}\)
bài 1
a)\(=\dfrac{16}{40}+\dfrac{15}{40}=\dfrac{31}{40}\)
b)\(=\dfrac{7}{6}-\dfrac{4}{6}=\dfrac{3}{6}=\dfrac{1}{2}\)
c)\(=\dfrac{30}{9}=\dfrac{10}{3}\)
d)\(=\dfrac{8}{5}\times\dfrac{7}{4}=\dfrac{56}{20}=\dfrac{14}{5}\)
a,2/9+1/6=7/18
b,5/6-4/7=11/42
c,3/8.6/15=3/20
d,7/12:4/7=49/48
e,4/7:3=4/21
a) \(\dfrac{1}{2}-\dfrac{1}{6}=\dfrac{3}{6}-\dfrac{1}{6}=\dfrac{3-1}{6}=\dfrac{2}{6}=\dfrac{1}{3}\)
b) \(\dfrac{3}{4}-\dfrac{5}{8}=\dfrac{12}{8}-\dfrac{5}{8}=\dfrac{12-5}{8}=\dfrac{7}{8}\)
c) \(\dfrac{7}{10}-\dfrac{2}{5}=\dfrac{7}{10}-\dfrac{4}{10}=\dfrac{7-4}{10}=\dfrac{3}{10}\)
d) \(\dfrac{7}{12}-\dfrac{1}{3}=\dfrac{7}{12}-\dfrac{4}{12}=\dfrac{7-4}{12}=\dfrac{3}{12}=\dfrac{1}{4}\)
a) \(\dfrac{1}{3}\)
b)\(\dfrac{1}{8}\)
c)\(\dfrac{3}{10}\)
d)\(\dfrac{3}{12}\)