Tính hợp lý a) (9/16 + 8/-27) + (1 + 7/16 + -19/27) b) (13/5 7/16) - (15/16 - 6/15)

* Hướng dẫn giải

a)

$\begin{array}{l}\left(\frac{9}{16}+\frac{8}{-27}\right)+\left(1+\frac{7}{16}+\frac{-19}{27}\right)\\ =\frac{9}{16}+\frac{8}{-27}+1+\frac{7}{16}+\frac{-19}{27}\\ =\left(\frac{9}{16}+\frac{7}{16}\right)+\left(\frac{-8}{27}+\frac{-19}{27}\right)+1\\ =1+\left(-1\right)+1=1\end{array}$

b) 

$\begin{array}{l}\left(\frac{13}{5}+\frac{7}{16}\right)-\left(\frac{15}{16}-\frac{6}{15}\right)\\ =\frac{13}{5}+\frac{7}{16}-\frac{15}{16}+\frac{2}{5}\\ =\left(\frac{13}{5}+\frac{2}{5}\right)+\left(\frac{7}{16}-\frac{15}{16}\right)\\ =3+\frac{-1}{2}=\frac{5}{2}\end{array}$