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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) \(\dfrac{3}{4}=\dfrac{3\cdot5}{4\cdot5}=\dfrac{15}{20}\\ \dfrac{2}{5}=\dfrac{2\cdot4}{5\cdot4}=\dfrac{8}{20}\)
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) năm phần bảy
hai mươi lăm phần một trăm
chín mươi mốt phần ba tám
sáu mươi phần mười bảy
tám mươi lăm phần một nghìn
b) tử: 5,25,91,60,85
mẫu: 7,100,38,17,1000
`a,3/10=0,3`
`3/100=0,03`
`4 25/100=4 1/4=4,25`
`2002/1000=2,002`
`b,1/4=0,25`
`3/5=0,6`
`7/8=0,875`
`1 1/2=1,5`
\(\dfrac{3}{5}và\dfrac{15}{25}và\dfrac{21}{35};\dfrac{5}{8}và\dfrac{20}{32}\)
\(\dfrac{3}{5}=\dfrac{9}{15}=\dfrac{15}{25}=\dfrac{21}{35}\\ \dfrac{5}{8}=\dfrac{20}{32}\)
a, \(\dfrac{3}{4}\) = \(\dfrac{3\times5}{4\times5}\) = \(\dfrac{15}{20}\) \(\dfrac{5}{7}\) = \(\dfrac{5\times3}{7\times3}\) = \(\dfrac{15}{21}\)
Vì \(\dfrac{15}{20}\) > \(\dfrac{15}{21}\) nên \(\dfrac{3}{4}\) > \(\dfrac{5}{7}\)
b, \(\dfrac{2}{7}\) = \(\dfrac{2\times2}{7\times2}\) = \(\dfrac{4}{14}\) < \(\dfrac{4}{9}\)
Vậy \(\dfrac{2}{7}\) < \(\dfrac{4}{9}\)
c, \(\dfrac{5}{8}\) < 1 < \(\dfrac{8}{5}\)
Vậy \(\dfrac{5}{8}\) < \(\dfrac{8}{5}\)
Ta có mẫu số chung là 360
\(->\) \(\dfrac{4}{15}=\dfrac{4x24}{15x24}=\dfrac{96}{360}\)
\(->\) \(\dfrac{5}{72}=\dfrac{5x5}{72x5}=\dfrac{25}{360}\)
\(->\) \(\dfrac{96}{360}+\dfrac{25}{360}=\dfrac{96+25}{360}=\dfrac{121}{360}\)
TL:
a) \(\dfrac{5}{6}\);\(\dfrac{9}{8}\);\(\dfrac{17}{18}\)
b) \(\dfrac{1}{2}\);\(\dfrac{5}{8}\);\(\dfrac{3}{4}\)