Tính bằng cách thuận tiện:

\(\frac{8}{{10}}\,\, \times \,\,80\,\, \times \,\,75\,\, \times \,\,\frac{2}{3}\)

= \(\frac{{8\,\, \times \,\,80\,\, \times \,\,75\,\, \times \,\,2}}{{10\,\, \times \,\,3}}\)

= \(\frac{{8\,\, \times \,\,8\,\, \times \,\,10\,\, \times \,\,25\,\, \times \,\,3\,\, \times \,\,2}}{{10\,\, \times \,\,3\,\,}}\)

= 8 × 8 × 25 × 2 = 3 200

\(\frac{{29}}{{100}}\,\, \times \,\,71\,\, + \,\,\frac{{29}}{{100}}\,\, \times \,\,29\)

= \(\frac{{29}}{{100}}\,\, \times \,\,\left( {71\,\, + \,29} \right)\)

= \(\frac{{29}}{{100}}\,\, \times \,\,100\)

= 29