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\(a)\) Mẫu số chung: 45.
\(\dfrac{2}{5}=\dfrac{2\times7}{5\times7}=\dfrac{14}{45}\\ \dfrac{13}{15}=\dfrac{13\times3}{15\times3}=\dfrac{39}{45}\\ \dfrac{19}{45}\)
b) Mẫu số chung: 16.
\(\dfrac{1}{2}=\dfrac{1\times8}{2\times8}=\dfrac{8}{16}\\ \dfrac{3}{8}=\dfrac{3\times2}{8\times2}=\dfrac{6}{16}\\ \dfrac{5}{4}=\dfrac{5\times4}{4\times4}=\dfrac{\dfrac{20}{16}\\ 7}{16}\)
a)
MSC: 35
\(\dfrac{4}{7}=\dfrac{4\times5}{7\times5}=\dfrac{20}{35}\)
\(\dfrac{28}{35}\) giữ nguyên
b)
MSC: 100
\(\dfrac{13}{20}=\dfrac{13\times5}{20\times5}=\dfrac{65}{100}\)
c)
MSC: 24
\(\dfrac{5}{6}=\dfrac{5\times4}{6\times4}=\dfrac{20}{24}\)
\(\dfrac{9}{8}=\dfrac{9\times3}{8\times3}=\dfrac{27}{24}\)
a, 4/7 và 28/35
ta có :
4/7=20/35
28/35
b13/20 và 32/100
ta có :
13/20=65/100
32/100
c,5/6,9/8 và 11/24
ta có :
5/6=20/24
9/8=27/24
11/24
Bài 1:
a)
\(\dfrac{1}{2}=\dfrac{1\times6}{2\times6}=\dfrac{6}{12}\)
\(\dfrac{2}{3}=\dfrac{2\times4}{3\times4}=\dfrac{8}{12}\)
\(\dfrac{3}{4}=\dfrac{3\times3}{4\times3}=\dfrac{9}{12}\)
b)
\(\dfrac{1}{3}=\dfrac{1\times15}{3\times15}=\dfrac{15}{45}\)
\(\dfrac{2}{15}=\dfrac{2\times3}{15\times3}=\dfrac{6}{45}\)
\(\dfrac{4}{45}\) (giữ nguyên)
c)
\(\dfrac{1}{8}=\dfrac{1\times3}{8\times3}=\dfrac{3}{24}\)
\(\dfrac{2}{3}=\dfrac{2\times8}{3\times8}=\dfrac{16}{24}\)
\(\dfrac{5}{2}=\dfrac{5\times12}{2\times12}=\dfrac{60}{24}\)
d)
\(\dfrac{2}{7}=\dfrac{2\times4}{7\times4}=\dfrac{8}{28}\)
\(\dfrac{9}{4}=\dfrac{9\times7}{4\times7}=\dfrac{63}{28}\)
\(\dfrac{5}{28}\) (giữ nguyên)
Bài 2:
a)
\(4=\dfrac{4}{1}=\dfrac{4\times12}{1\times12}=\dfrac{48}{12}\)
\(\dfrac{9}{4}=\dfrac{9\times3}{4\times3}=\dfrac{27}{12}\)
b)
\(\dfrac{5}{8}=\dfrac{5\times30}{8\times30}=\dfrac{150}{240}\)
\(\dfrac{25}{30}=\dfrac{5}{6}=\dfrac{5\times40}{6\times40}=\dfrac{200}{240}\)
\(2=\dfrac{2}{1}=\dfrac{2\times240}{1\times240}=\dfrac{480}{240}\).
a) \(\dfrac{2}{3}=\dfrac{2.8}{3.8}=\dfrac{16}{24}\)
\(\dfrac{5}{8}=\dfrac{5.3}{8.3}=\dfrac{15}{24}\)
b) \(\dfrac{1}{4}=\dfrac{1.3}{4.3}=\dfrac{3}{12}\)
\(\dfrac{7}{12}=\dfrac{7.1}{12.1}=\dfrac{7}{12}\)
c) \(\dfrac{5}{6}=\dfrac{5.4}{6.4}=\dfrac{20}{24}\)
\(\dfrac{3}{8}=\dfrac{3.3}{8.3}=\dfrac{9}{24}\)
a) 23=2.83.8=162423=2.83.8=1624
58=5.38.3=152458=5.38.3=1524
b) 14=1.34.3=31214=1.34.3=312
712=7.112.1=712712=7.112.1=712
c) 56=5.46.4=202456=5.46.4=2024
38=3.38.3=924
a)\(\dfrac{3}{7}=\dfrac{3.8}{7.8}=\dfrac{24}{56};\dfrac{5}{8}=\dfrac{5.7}{8.7}=\dfrac{35}{56}\)
b)\(\dfrac{7}{10}=\dfrac{7.2}{10.2}=\dfrac{14}{20};\dfrac{3}{20}\)
c)\(\dfrac{9}{20}=\dfrac{9.9}{20.9}=\dfrac{81}{180};\dfrac{2}{9}=\dfrac{2.20}{9.20}=\dfrac{40}{180}\)
a: \(\dfrac{11}{42}=\dfrac{11\cdot1}{42\cdot1}=\dfrac{11}{42}\)
\(\dfrac{5}{6}=\dfrac{5\cdot7}{6\cdot7}=\dfrac{35}{42}\)
b: \(\dfrac{40}{7}=\dfrac{40\cdot4}{7\cdot4}=\dfrac{160}{28}\)
\(\dfrac{10}{28}=\dfrac{10\cdot1}{28\cdot1}=\dfrac{10}{28}\)
c: \(\dfrac{4}{15}=\dfrac{4\cdot4}{15\cdot4}=\dfrac{16}{60}\)
\(\dfrac{14}{60}=\dfrac{14\cdot1}{60\cdot1}=\dfrac{14}{60}\)
a)\(\dfrac{11}{42}=\dfrac{35}{42}\)
b) \(\dfrac{160}{28}=\dfrac{10}{28}\)
c) \(\dfrac{16}{60}=\dfrac{14}{60}\)
a) \(\dfrac{3}{4}=\dfrac{3\cdot5}{4\cdot5}=\dfrac{15}{20}\\ \dfrac{2}{5}=\dfrac{2\cdot4}{5\cdot4}=\dfrac{8}{20}\)
b) \(\dfrac{5}{12}=\dfrac{5\cdot3}{12\cdot3}=\dfrac{15}{36}\\ \dfrac{11}{36}=\dfrac{11}{36}\)
c) \(\dfrac{2}{3}=\dfrac{2\cdot4\cdot5}{3\cdot4\cdot5}=\dfrac{40}{60}\\ \dfrac{3}{4}=\dfrac{3\cdot3\cdot5}{4\cdot3\cdot5}=\dfrac{45}{60}\\ \dfrac{4}{5}=\dfrac{4\cdot3\cdot4}{5\cdot3\cdot4}=\dfrac{48}{60}\)
a) \(\dfrac{3}{4}\) và \(\dfrac{2}{5}\)
Mẫu số chung: 20
\(\dfrac{3}{4}=\dfrac{3.5}{4.5}=\dfrac{15}{20}\)
\(\dfrac{2}{5}=\dfrac{2.4}{5.4}=\dfrac{8}{20}\)
b) \(\dfrac{5}{12}\) và \(\dfrac{11}{36}\)
Mẫu số chung: 36
\(\dfrac{5}{12}=\dfrac{5.3}{12.3}=\dfrac{15}{36}\)
c) \(\dfrac{2}{3};\dfrac{3}{4}\) và \(\dfrac{4}{5}\)
Mẫu số chung: 60
\(\dfrac{2}{3}=\dfrac{2.20}{3.20}=\dfrac{40}{60}\\ \dfrac{3}{4}=\dfrac{3.15}{4.15}=\dfrac{45}{60}\\ \dfrac{4}{5}=\dfrac{4.12}{5.12}=\dfrac{48}{60}\)
a) \(\dfrac{5}{6}=\dfrac{20}{24}\)
b) \(\dfrac{7}{15}=\dfrac{21}{45}\)
c) \(\dfrac{2}{3}=\dfrac{200}{300}\)