Tính bằng cách thuận tiện

a) \(\frac{3}{{14}} \times \frac{{28}}{9} \times \frac{{14}}{3}\)

= \((\frac{3}{{14}} \times \frac{{14}}{3}) \times \frac{{28}}{9}\)

= \(1 \times \frac{{28}}{9}\)

= \(\frac{{28}}{9}\)

b) \(\frac{4}{7} \times \frac{5}{8} + \frac{5}{8} \times \frac{4}{7}\)

= \(\frac{4}{7} \times (\frac{5}{8} + \frac{5}{8})\)

= \(\frac{4}{7} \times \frac{5}{4}\)

= \(\frac{5}{7}\)