Điền dấu >; <; = thích hợp vào chỗ chấm:   a) 1/4 +3/5.... 31/20 - 3/5

a)

Vì: \(\frac{1}{4} + \frac{3}{5} = \frac{{17}}{{20}};\frac{{31}}{{20}} - \frac{3}{5} = \frac{{19}}{{20}}\)

So sánh: \(\frac{{17}}{{20}} < \frac{{19}}{{20}}\)

Vậy: \(\frac{1}{4} + \frac{3}{5} < \frac{{31}}{{20}} - \frac{3}{5}\)

b)

Vì: \(\frac{{14}}{{25}} \times \frac{5}{2} = \frac{7}{5};\frac{6}{5}:\frac{1}{7} = \frac{6}{5} \times \frac{7}{1} = \frac{{42}}{5}\)

So sánh: \(\frac{7}{5} < \frac{{42}}{5}\)

Vậy: \(\frac{{14}}{{25}} \times \frac{5}{2} < \frac{6}{5}:\frac{1}{7}\)