Question

Tính bằng cách hợp lý :

[(3/10- 4/15 - 7/20).5/19] / {[1/14+1/7- (-3) /35].[(-4)/3]

Answer 1

\(\dfrac{\left[\left(\dfrac{3}{10}-\dfrac{4}{15}-\dfrac{7}{20}\right)\cdot\dfrac{5}{19}\right]}{\left[\dfrac{1}{14}+\dfrac{1}{7}-\dfrac{\left(-3\right)}{35}\right]\cdot\left(-\dfrac{4}{3}\right)}\)

\(=\dfrac{\left(\dfrac{18}{60}-\dfrac{16}{60}-\dfrac{21}{60}\right)\cdot\dfrac{5}{19}}{\left(\dfrac{5}{70}+\dfrac{10}{70}+\dfrac{6}{70}\right)\cdot\dfrac{-4}{3}}=\dfrac{\dfrac{-19}{60}\cdot\dfrac{5}{19}}{\dfrac{21}{70}\cdot\dfrac{-4}{3}}\)

\(=-\dfrac{1}{12}:\dfrac{-2}{5}=\dfrac{1}{12}\cdot\dfrac{5}{2}=\dfrac{5}{24}\)