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\(\dfrac{3}{6}=\dfrac{3:3}{6:3}=\dfrac{1}{2}\\ \dfrac{18}{24}=\dfrac{18:6}{24:6}=\dfrac{3}{4}\\ \dfrac{5}{35}=\dfrac{5:5}{35:5}=\dfrac{1}{7}\\ \dfrac{40}{90}=\dfrac{40:10}{90:10}=\dfrac{4}{9}\\ \dfrac{75}{30}=\dfrac{75:15}{30:15}=\dfrac{5}{2}\)
\(\dfrac{3}{6}=\dfrac{3:3}{6:3}=\dfrac{1}{2}\\ \dfrac{18}{24}=\dfrac{18:6}{24:6}=\dfrac{3}{4}\\ \dfrac{5}{35}=\dfrac{5:5}{35:5}=\dfrac{1}{7}\\ \dfrac{40}{90}=\dfrac{40:10}{90:10}=\dfrac{4}{9}\\ \dfrac{75}{30}=\dfrac{75:15}{30:15}=\dfrac{5}{2}\)
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
1,
Ta có:
\(\dfrac{73}{75}=1-\dfrac{2}{75}\)
\(\dfrac{77}{79}=1-\dfrac{2}{79}\)
So sánh phân số \(\dfrac{2}{75}\) và \(\dfrac{2}{79}\)
Vì \(75< 79\) nên \(\dfrac{1}{75}>\dfrac{1}{79}\)
Vậy \(1-\dfrac{2}{75}< 1-\dfrac{2}{79}\)
Hay \(\dfrac{73}{75}< \dfrac{77}{79}\)
2,
Vì \(\dfrac{53}{100}>\dfrac{47}{100}>\dfrac{47}{106}\) nên \(\dfrac{53}{100}>\dfrac{47}{106}\)
3,
Ta có:
\(\dfrac{81}{79}=1+\dfrac{2}{79}\)
\(\dfrac{65}{63}=1+\dfrac{2}{63}\)
So sánh phân số \(\dfrac{2}{79}\) và \(\dfrac{2}{63}\)
Vì \(79>63\) nên \(\dfrac{81}{79}< \dfrac{65}{63}\)
Hay \(\Rightarrow1+\dfrac{2}{79}< 1+\dfrac{2}{63}\)
Vậy \(\dfrac{81}{79}< \dfrac{65}{63}\)
4,
\(\dfrac{48}{47}>1>\dfrac{84}{85}\)
Vậy \(\dfrac{48}{47}>\dfrac{84}{85}\)
\(a.\)\(\dfrac{5}{10}=\dfrac{5:5}{10:5}=\dfrac{1}{2};\dfrac{25}{75}=\dfrac{25:25}{75:25}=\dfrac{1}{3}.\)
Quy đồng: \(\dfrac{1}{2}=\dfrac{1\times3}{2\times3}=\dfrac{3}{6};\dfrac{1}{3}=\dfrac{1\times2}{3\times2}=\dfrac{2}{6}.\)
\(b.\)\(\dfrac{42}{56}=\dfrac{42:14}{56:14}=\dfrac{3}{4};\dfrac{18}{48}=\dfrac{18:6}{48:6}=\dfrac{3}{8}.\)
Quy đồng: \(\dfrac{3}{4}=\dfrac{3\times2}{4\times2}=\dfrac{6}{8};\) Giữ nguyên \(\dfrac{3}{8}.\)