Tính bằng cách thuận tiện. a) 3/5 + 14/7 + 4/10 b)  1/7 + 2/7 + 3/7 + 4/7 + 5/7 + 6/7

\[\begin{array}{l}\frac{3}{5}\,\, + \,\,\frac{{14}}{7}\,\, + \,\,\frac{4}{{10}}\\ = \,\,(\frac{3}{5}\,\, + \,\,\frac{4}{{10}})\,\, + \,\,\frac{{14}}{7}\end{array}\]

= 1 + 2

= 3

\[\begin{array}{l}\frac{1}{7}\,\, + \,\,\frac{2}{7}\,\, + \,\,\frac{3}{7}\,\, + \,\,\frac{4}{7}\,\, + \,\,\frac{5}{7}\,\, + \,\,\frac{6}{7}\\ = \,\,(\frac{1}{7}\,\, + \,\,\frac{6}{7})\,\, + \,\,(\frac{2}{7}\,\, + \,\,\frac{5}{7})\,\, + \,\,(\frac{3}{7}\,\, + \,\,\frac{4}{7})\end{array}\]

= 1 + 1 + 1

= 3