Tính: \(\displaystyle \left( { - 3,2} \right).{{ - 15} \over {64}} + \left( {0,8 - 2{4 \over {15}}} \right):3{2 \over 3}.\)

* Hướng dẫn giải

\( \displaystyle \left( { - 3,2} \right).{{ - 15} \over {64}} + \left( {0,8 - 2{4 \over {15}}} \right):3{2 \over 3}\)

\( \displaystyle = {{ - 32} \over {10}}.{{ - 15} \over {64}} + \left( {{4 \over {5}} - {{34} \over {15}}} \right):{{11} \over 3}\)

\( \displaystyle = {{ - 32.(-15)} \over 10.64}+ \left( {{{12} \over {15}} - {{34} \over {15}}} \right):{{11} \over 3}\)

\( \displaystyle = {3 \over 4} + {{ - 22} \over {15}}.{{3} \over {11}} ={{ 3} \over 4} + {{ - 4} \over {10}}\)

\( \displaystyle = {{15} \over {20}} + {{ - 8} \over {20}} = {15+(-8) \over {20}}={7 \over {20}}\)