Tính a) -1,6 : (1 + 2/3) b) 7/30 + -12/37 + 5/25 + -25/37 + 23/30

* Hướng dẫn giải

a) $-\text{1,6:}\left(\text{1}+\frac{\text{2}}{\text{3}}\right)=\frac{-16}{10}:\left(\frac{3}{3}+\frac{2}{3}\right)=\frac{-16}{10}:\frac{5}{3}$$=\frac{-16}{10}.\frac{3}{5}=\frac{-16.3}{10.5}=\frac{-8.3}{5.5}=\frac{-24}{25}.$

b) $\frac{7}{30}+\frac{-12}{37}+\frac{5}{25}+\frac{-25}{37}+\frac{23}{30}$ $=\left(\frac{7}{30}+\frac{23}{30}\right)+\left(\frac{-12}{37}+\frac{-25}{37}\right)+\frac{5}{25}$ $=\frac{30}{30}+\frac{-37}{37}+\frac{1}{5}=1+\left(-1\right)+\frac{1}{5}=\frac{1}{5}.$