Thực hiện phép tính: 2 1/5 : (1 2/5 + (-3)/10) - 2/5

Giải SBT Toán 6 Bài 7: Hỗn số

Bài 5 trang 32 SBT Toán 6 Tập 2:

a) $2\frac{1}{5}:\left(1\frac{2}{5}+\frac{-3}{10}\right)-\frac{2}{5}$;

b) $\frac{-15}{4}.3\frac{1}{3}-1\frac{3}{4}+\frac{-7}{8}$.

Lời giải:

a)

$2\frac{1}{5}:\left(1\frac{2}{5}+\frac{-3}{10}\right)-\frac{2}{5}=\frac{11}{5}:\left(\frac{7}{5}+\frac{-3}{10}\right)-\frac{2}{5}=\frac{11}{5}:\left(\frac{14}{10}+\frac{-3}{10}\right)-\frac{2}{5}=\frac{11}{5}:\frac{11}{10}-\frac{2}{5}=\frac{11}{5}.\frac{10}{11}-\frac{2}{5}=\frac{10}{5}-\frac{2}{5}=\frac{8}{5}$

b)

$\frac{-15}{4}.3\frac{1}{3}-1\frac{3}{4}+\frac{-7}{8}=\frac{-15}{4}.\frac{10}{3}-\frac{7}{4}+\frac{-7}{8}=\frac{-15.10}{4.3}-\frac{7}{4}+\frac{-7}{8}=\frac{-25}{2}-\frac{7}{4}+\frac{-7}{8}=\frac{-100}{8}+\frac{-14}{8}+\frac{-7}{8}=\frac{-121}{8}$