Tính hợp lí: a) -10/3 + 13/10 - 1/6 + 7/10 b) 1 - 20/6 + 39/30 - 4/24 + 35/50

* Hướng dẫn giải

$a)\frac{-10}{3}+\frac{13}{10}-\frac{1}{6}+\frac{7}{10}=\left(\frac{{\displaystyle 13}}{{\displaystyle 10}}+\frac{{\displaystyle 7}}{{\displaystyle 10}}\right)+\left(\frac{{\displaystyle -10}}{{\displaystyle 3}}+\frac{{\displaystyle -1}}{{\displaystyle 6}}\right)$$=2-\frac{{\displaystyle 7}}{{\displaystyle 2}}=\frac{{\displaystyle -3}}{{\displaystyle 2}}$

$b)1-\frac{20}{6}+\frac{39}{30}-\frac{4}{24}+\frac{4}{24}$$=1-\frac{10}{3}+\frac{13}{10}-\frac{1}{6}+\frac{7}{10}=\frac{-1}{2}$