Tính bằng cách thuận tiện. a) 11/16 x 25 x 16 x 34/25

a) \(\frac{{11}}{{16}} \times 25 \times 16 \times \frac{{34}}{{25}}\)

= \(\left( {\frac{{11}}{{16}} \times 16} \right) \times \left( {25 \times \frac{{34}}{{25}}} \right)\)

= 11 × 34

= 374

b) \(\frac{7}{{15}} \times \frac{{31}}{{12}} + \frac{{17}}{{12}} \times \frac{7}{{15}}\)

= \(\frac{7}{{15}} \times \left( {\frac{{31}}{{12}} + \frac{{17}}{{12}}} \right)\)

= \(\frac{7}{{15}} \times \frac{{48}}{{12}}\)

= \[\frac{7}{{15}} \times 4\] = \(\frac{{28}}{{15}}\)