Phân số nào dưới đây bé hơn 1?

\(\frac{3}{4} = \frac{{3 \times 6}}{{4 \times 6}} = \frac{{18}}{{24}}\); \(\frac{5}{6} = \frac{{5 \times 4}}{{6 \times 4}} = \frac{{20}}{{24}}\)

\(\frac{2}{3} = \frac{{2 \times 8}}{{3 \times 8}} = \frac{{16}}{{24}}\); \(\frac{7}{8} = \frac{{7 \times 3}}{{8 \times 3}} = \frac{{21}}{{24}}\)

Vì 16 < 18 < 20 < 21 nên \(\frac{{16}}{{24}} < \frac{{18}}{{24}} < \frac{{20}}{{24}} < \frac{{21}}{{24}}\) hay \(\frac{2}{3} < \frac{3}{4} < \frac{5}{6} < \frac{7}{8}\)

Vậy Cường về đích đầu tiên, Dũng về đích cuối cùng

a) \(\frac{{48}}{{56}} = \frac{{24}}{{28}} = \frac{6}{7} = \frac{{36}}{{42}}\)                                         b) \(\frac{{80}}{{120}} = \frac{{20}}{{30}} = \frac{4}{6} = \frac{{40}}{{60}}\)