Tính giá trị của mỗi biểu thức sau: a) (0,25 - 5/6).1,6 - 1/3 b) 3 - 2.[0,5 + (0,25 - 1/6)]

* Hướng dẫn giải

$$\begin{gathered} a) \left(0,25-\frac{5}{6}\right).1,6+\frac{-1}{3} \\ =\left(\frac{1}{4}-\frac{5}{6}\right).\frac{8}{5}+\frac{-1}{3} \\ =\left(\frac{3}{12}-\frac{10}{12}\right).\frac{8}{5}+\frac{-1}{3} \\ =\frac{-7}{12}.\frac{8}{5}+\frac{-1}{3} \\ =\frac{-14}{15}+\frac{-1}{3} \\ =\frac{-14}{15}+\frac{-5}{15} \\ =\frac{-19}{15} \\ b) 3-2.\left[0,5+\left(0,25-\frac{1}{6}\right)\right] \\ =3-2.\left[\frac{1}{2}+\left(\frac{1}{4}-\frac{1}{6}\right)\right] \\ =3-2.\left[\frac{1}{2}+\left(\frac{3}{12}-\frac{2}{12}\right)\right] \\ =3-2.\left(\frac{1}{2}+\frac{1}{12}\right) \\ =3-2.\left(\frac{6}{12}+\frac{1}{12}\right) \\ =3-2.\frac{7}{12}=3-\frac{7}{6} \\ =\frac{18}{6}-\frac{7}{6}=\frac{11}{6} \end{gathered}$$