Tính nhanh a) 15/12 - ( -5/13) - 3/12 - 18/13

10/13

Tính nhanh

a) \(\frac{{15}}{{12}} - \left( { - \frac{5}{{13}}} \right) - \frac{3}{{12}} - \frac{{18}}{{13}}\)

b) \(5,3\,.\,4,7 + \left( { - 1,7} \right)\,.\,5,3 - 5,9\)

c) \(\left( {8 - 1,5 + \frac{2}{7}} \right) + \left( {6 - \frac{4}{7} + 1\frac{1}{2}} \right) - \left( {3 - 1\frac{2}{7}} \right)\)

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Giải thích

a) \[\left( {-\,3,8} \right) + \left( {-\,5,7} \right) + 3,8 + \left( {-\,4,3} \right) + 3\]

\[ = \left[ {\left( {-\,3,8} \right) + 3,8} \right] + \left[ {\left( {-\,5,7} \right) + \left( {-\,4,3} \right)} \right] + 3\]

\[ = 0 + \left( {-\,10} \right) + 3 = -7\].

b) \(\frac{{ - 3}}{{11}}.\frac{5}{9} + \frac{4}{9}.\frac{{ - 3}}{{11}} = \frac{{ - 3}}{{11}}.\,\left( {\frac{5}{9} + \frac{4}{9}} \right) = \frac{{ - 3}}{{11}}.1 = \frac{{ - 3}}{{11}}\);

c) \(\left( {7 - \frac{2}{3} + 2\frac{1}{5}} \right) - \left( {5 + \frac{5}{3} - \frac{3}{5}} \right) - \left( {3 - \frac{7}{3} + \frac{{14}}{5}} \right)\)

\( = 7 - \frac{2}{3} + 2\frac{1}{5} - 5 - \frac{5}{3} + \frac{3}{5} - 3 + \frac{7}{3} - \frac{{14}}{5}\)

\( = \left( {7 - 5 - 3} \right) + \left( { - \frac{2}{3} - \frac{5}{3} + \frac{7}{3}} \right) + \left( {\frac{{11}}{5} + \frac{3}{5} - \frac{{14}}{5}} \right)\)

\( = \left( { - 1} \right) + 0 + 0 = - 1\).