Nối phép tính đúng: 4/7 - 2/21

Nối

Giải thích

\[\frac{{29}}{{42}} - \frac{2}{7} = \frac{{29}}{{42}} - \frac{{12}}{{42}} = \frac{{17}}{{42}}\]

\[\frac{6}{7} - \frac{5}{{42}} = \frac{{36}}{{42}} - \frac{5}{{42}} = \frac{{31}}{{42}}\]

Vậy \[\frac{{17}}{{42}} < ..... < \frac{{31}}{{42}}\]

Xét các phép tính:

\[\frac{4}{7} - \frac{2}{{21}} = \frac{{24}}{{42}} - \frac{4}{{42}} = \frac{{20}}{{42}}\];                             \[\frac{5}{6} - \frac{1}{{21}} = \frac{{35}}{{42}} - \frac{2}{{42}} = \frac{{33}}{{42}}\]

\[\frac{{31}}{{42}} - \frac{1}{{14}} = \frac{{31}}{{42}} - \frac{3}{{42}} = \frac{{28}}{{42}}\];                             \[\frac{4}{3} - \frac{9}{{21}} = \frac{{56}}{{42}} - \frac{{18}}{{42}} = \frac{{38}}{{42}}\]

Vậy các phép tính thỏa mãn là: \[\frac{4}{7} - \frac{2}{{21}}\]; \[\frac{{31}}{{42}} - \frac{1}{{14}}\]