Question

Thực hiệp phép tính:

a) \(\dfrac{2}{5}.\left(\dfrac{2}{3}-\dfrac{1}{4}\right)+\dfrac{1}{2}\)

b) 1,8:\(\dfrac{27}{-20}+\left(75\%-\dfrac{5}{16}\right):3\dfrac{1}{2}\)

Answer 1

a) \(\dfrac{2}{5}.\left(\dfrac{2}{3}-\dfrac{1}{4}\right)+\dfrac{1}{2}\\ =\dfrac{2}{5}.\left(\dfrac{8}{12}-\dfrac{3}{12}\right)+\dfrac{1}{2}\\ =\dfrac{2}{5}.\dfrac{5}{12}+\dfrac{1}{2}\\ =\dfrac{1}{6}+\dfrac{1}{2}\\ =\dfrac{1}{6}+\dfrac{3}{6}\\ =\dfrac{2}{3}\)

Answer 2

b) \(1,8:\dfrac{27}{-20}+\left(75\%-\dfrac{5}{16}\right):3\dfrac{1}{2}\\ =\dfrac{9}{5}:\dfrac{-27}{20}+\left(\dfrac{3}{4}-\dfrac{5}{16}\right):\dfrac{7}{2}\\ =\dfrac{9}{5}.\dfrac{-20}{27}+\left(\dfrac{12}{16}-\dfrac{5}{16}\right):\dfrac{7}{2}\\ =\dfrac{-4}{3}+\dfrac{7}{16}:\dfrac{7}{2}\\ =\dfrac{-4}{3}+\dfrac{7}{16}.\dfrac{2}{7}\\ =\dfrac{-4}{3}+\dfrac{1}{8}\\ =\dfrac{-32}{24}+\dfrac{3}{24}\\ =\dfrac{-29}{24}\)