Bài 2 trang 38 Toán 6 Tập 2 | Cánh diều Giải Toán lớp 6

Bài 2 trang 38 Toán 6 Tập 2:

a) $\frac{2}{9}+\frac{-3}{10}+\frac{-7}{10}$

b) $\frac{-11}{6}+\frac{2}{5}+\frac{-1}{6}$

c) $\frac{-5}{8}+\frac{12}{7}+\frac{13}{8}+\frac{2}{7}$

Lời giải

a) $\frac{2}{9}+\frac{-3}{10}+\frac{-7}{10}$

$=\frac{2}{9}+\left(\frac{-3}{10}+\frac{-7}{10}\right)$

$=\frac{2}{9}+\left(\frac{-3-7}{10}\right)$

$=\frac{2}{9}+\frac{-10}{10}$

$=\frac{2}{9}+\left(-1\right)$

$=\frac{2}{9}+\frac{-9}{9}$

$=\frac{2-9}{9}$

$=\frac{-7}{9}.$

b) $\frac{-11}{6}+\frac{2}{5}+\frac{-1}{6}$

$=\left(\frac{-11}{6}+\frac{-1}{6}\right)+\frac{2}{5}$

$=\left(\frac{-12}{6}\right)+\frac{2}{5}$

$=\left(-2\right)+\frac{2}{5}$

$=\frac{-10}{5}+\frac{2}{5}$

$=\frac{-10+2}{5}$

$=\frac{-8}{5}.$

c) $\frac{-5}{8}+\frac{12}{7}+\frac{13}{8}+\frac{2}{7}$

$=\left(\frac{-5}{8}+\frac{13}{8}\right)+\left(\frac{12}{7}+\frac{2}{7}\right)$

$=\left(\frac{-5+13}{8}\right)+\left(\frac{12+2}{7}\right)$

$=\frac{8}{8}+\frac{14}{7}$

$=1+2=3.$