Nó lừa đấyyyyy :"))

Tài khoản con Mai còn 4 coin thôiiiiiii

tách nhỏ câu hỏi ra 

Đổi 4h30'=4,5h

Gọi chiều dài quãng đường là a (a>0)
Theo bài ra ta có pt:\(\dfrac{a}{15}+\dfrac{a}{12}=4,5\\ \Rightarrow\dfrac{12a+15a}{180}=4,5\\ \Rightarrow27a=810\\ \Rightarrow a=30\left(km\right)\)

Bài 3:

a) \(\dfrac{3}{4}.\dfrac{16}{9}-\dfrac{7}{5}:\dfrac{-21}{20}=\dfrac{4}{3}-\dfrac{-4}{3}=\dfrac{8}{3}\)  

b) \(2\dfrac{1}{3}-\dfrac{1}{3}.\left[\dfrac{-3}{2}+\left(\dfrac{2}{3}+0,4.5\right)\right]\) 

\(=\dfrac{7}{3}-\dfrac{1}{3}.\left[\dfrac{-3}{2}+\left(\dfrac{2}{3}+\dfrac{2}{5}.5\right)\right]\) 

\(=\dfrac{7}{3}-\dfrac{1}{3}.\left[\dfrac{-3}{2}+\left(\dfrac{2}{3}+2\right)\right]\)

\(=\dfrac{7}{3}-\dfrac{1}{3}.\left[\dfrac{-3}{2}+\dfrac{8}{3}\right]\) 

\(=\dfrac{7}{3}-\dfrac{1}{3}.\dfrac{7}{6}\) 

\(=\dfrac{7}{3}-\dfrac{7}{18}\) 

\(=\dfrac{35}{18}\) 

c) \(\left(20+9\dfrac{1}{4}\right):2\dfrac{1}{4}=\left(20+\dfrac{37}{4}\right):\dfrac{9}{4}=\dfrac{117}{4}:\dfrac{9}{4}=13\) 

d) \(\left(6-2\dfrac{4}{5}\right).3\dfrac{1}{8}-1\dfrac{3}{5}:\dfrac{1}{4}\) 

\(=\left(6-\dfrac{14}{5}\right).\dfrac{25}{8}-\dfrac{8}{5}:\dfrac{1}{4}\) 

\(=\dfrac{16}{5}.\dfrac{25}{8}-\dfrac{32}{5}\) 

\(=10-\dfrac{32}{5}\) 

\(=\dfrac{18}{5}\) 

e) \(\dfrac{32}{15}:\left(-1\dfrac{1}{5}+1\dfrac{1}{3}\right)=\dfrac{32}{15}:\left(\dfrac{-6}{5}+\dfrac{4}{3}\right)=\dfrac{32}{15}:\dfrac{2}{15}=16\) 

g) \(0,2.\dfrac{15}{36}-\left(\dfrac{2}{5}+\dfrac{2}{3}\right):1\dfrac{1}{5}\) 

\(=\dfrac{1}{5}.\dfrac{5}{12}-\dfrac{16}{15}:\dfrac{6}{5}\) 

\(=\dfrac{1}{12}-\dfrac{8}{9}\) 

\(=\dfrac{-29}{36}\) 

h) \(1\dfrac{13}{15}.0,75-\left(\dfrac{8}{15}+0,25\right).\dfrac{24}{27}\) 

\(=\dfrac{28}{15}.\dfrac{3}{4}-\left(\dfrac{8}{15}+\dfrac{1}{4}\right).\dfrac{8}{9}\) 

\(=\dfrac{7}{5}-\dfrac{47}{60}.\dfrac{8}{9}\) 

\(=\dfrac{7}{5}-\dfrac{94}{135}\) 

\(=\dfrac{19}{27}\) 

g) \(5:\left(4\dfrac{3}{4}-1\dfrac{25}{28}\right)-1\dfrac{3}{8}:\left(\dfrac{3}{8}+\dfrac{9}{20}\right)\) 

\(=5:\left(\dfrac{19}{4}-\dfrac{53}{28}\right)-\dfrac{11}{8}:\dfrac{33}{40}\) 

\(=5:\dfrac{20}{7}-\dfrac{5}{3}\) 

\(=\dfrac{7}{4}-\dfrac{5}{3}\) 

\(=\dfrac{1}{12}\)

\(a\)) \(\dfrac{3}{4}.\dfrac{16}{9}-\dfrac{7}{5}:\dfrac{-21}{20}\)

\(=\dfrac{4}{3}-\dfrac{7}{5}.\dfrac{-20}{21}\)

\(=\dfrac{4}{3}-\dfrac{-4}{3}\)

\(=\dfrac{8}{3}\)

\(=2\dfrac{2}{3}\)

bài đâu

Bài đou bạn :)?

:D???????

lạc hậu

Câu 6:

6/9=2/3

18/48=3/8

72/84=6/7

1212/3939=4/13

108/216=1/2

Câu 6:

6/9=2/3

18/48=3/8

72/84=6/7

1212/3939=4/13

108/216=1/2

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