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Bài 2:
Số em biết bơi là \(\left(30-6\right):2=12\left(em\right)\)
Số em ch biết bơi là \(30-12=18\left(em\right)\)
Bài 3:
Số SGK là \(\left(1800+1000\right):2=1400\left(cuốn\right)\)
\(=\left(\dfrac{3+8}{12}\right)\cdot\dfrac{4}{5}=\dfrac{11}{12}\cdot\dfrac{4}{5}=\dfrac{44}{60}=\dfrac{11}{15}\)
\(\dfrac{3}{5}+\dfrac{4}{3}\times\dfrac{5}{6}=\dfrac{3}{5}+\dfrac{10}{9}=\dfrac{27}{45}+\dfrac{50}{45}=\dfrac{77}{45}\)
\(2-\dfrac{7}{6}+\dfrac{1}{3}=\dfrac{12}{6}-\dfrac{7}{6}+\dfrac{2}{6}=\dfrac{7}{6}\)
\(\dfrac{7}{6}\times3-\dfrac{3}{5}=\dfrac{7}{2}-\dfrac{3}{5}=\dfrac{35}{10}-\dfrac{6}{10}=\dfrac{29}{10}\)
a) \(\dfrac{3}{5}\times x=\dfrac{4}{7}\)
\(x=\dfrac{4}{7}\div\dfrac{3}{5}\)
\(x=\dfrac{20}{21}\)
b) \(\dfrac{1}{8}\div x=\dfrac{1}{5}\)
\(x=\dfrac{1}{8}\div\dfrac{1}{5}\)
\(x=\dfrac{5}{8}\)
a, 2/3 - 2/9 + 7/9 = 6/9 - 2/9 + 7/9 = 10/9
b, 7/6 + 3/5 : 6 = 7/6 + 3/5 x 1/6 = 7/6 + 1/10 = 70/60 + 6/10 = 76/10 = 38/5
c, x : 6/25 = 18
x = 18 x 6/25
x = 36/25
d, ( 2/5 + 4/7) : x = 17/5
29/35 : x = 17/5
x = 29/35 : 17/5
x = 29/119
\(a.\dfrac{2}{3}-\dfrac{2}{9}+\dfrac{7}{9}=\dfrac{6}{9}-\dfrac{2}{9}+\dfrac{7}{9}=\dfrac{4}{9}+\dfrac{7}{9}=\dfrac{11}{9}\\ b.\dfrac{7}{6}+\dfrac{3}{5}:6=\dfrac{7}{6}+\dfrac{3}{5}\times\dfrac{1}{6}=\dfrac{7}{6}+\dfrac{1}{10}=\dfrac{70}{60}+\dfrac{6}{60}=\dfrac{76}{60}=\dfrac{19}{15}\\ c.x:\dfrac{6}{25}=18\\ x=18\times\dfrac{6}{25}\\ x=\dfrac{108}{25}\\ d.\left(\dfrac{2}{5}+\dfrac{4}{7}\right):x=\dfrac{17}{5}\\ \dfrac{34}{35}:x=\dfrac{7}{5}\\ x=\dfrac{34}{35}:\dfrac{7}{5}\\ x=\dfrac{34}{49}\)
2 x 3/5 = 6/5
2×\(\frac{3}{5}\)
=\(\frac{6}{5}\)
=1,2
Học tốt~