Thực hiện phép tính: a) (2/7 : 5/4) . (5/8 :2) b) (11/15 . 35/44)

* Hướng dẫn giải

a) $\left(\frac{2}{7}:\frac{5}{4}\right).\left(\frac{5}{8}:2\right)=\left(\frac{2}{7}.\frac{4}{5}\right).\left(\frac{5}{8}.\frac{1}{2}\right)=\frac{8}{35}.\frac{5}{16}=\frac{1}{14}$

b) $\left(\frac{11}{15}.\frac{35}{44}\right):\left(7.\frac{13}{4}\right)=\frac{7}{12}:\frac{91}{4}=\frac{7}{12}.\frac{4}{91}=\frac{1}{39}$