PHẦN II. TỰ LUẬN

Thực hiện phép tính (tính hợp lí nếu có thể):

    a) \(1,25.6.\left( { - 8} \right)\);                  b) \(\frac{6}{5} - \frac{1}{5}:\frac{3}{{10}}\);

    c) \(12,3 - 5,48 - 4,52 - 0,3\);                     d) \(\frac{4}{9}.\frac{{ - 7}}{{26}} + \frac{{45}}{{ - 26}}.\frac{4}{9} + \frac{1}{3}\).

a) \(1,25.6.\left( { - 8} \right)\)

\( = \left[ {1,25.\left( { - 8} \right)} \right].6\)

\( = \left( { - 10} \right).6\)

\( =  - 60\).

b) \(\frac{6}{5} - \frac{1}{5}:\frac{3}{{10}}\)\( = \frac{6}{5} - \frac{1}{5}.\frac{{10}}{3}\)

\( = \frac{6}{5} - \frac{2}{3}\)\( = \frac{{18}}{{15}} - \frac{{10}}{{15}} = \frac{8}{{15}}\).

c) \(12,3 - 5,48 - 4,52 - 0,3\)

\( = \left( {12,3 - 0,3} \right) - \left( {5,48 + 4,52} \right)\)

\( = \left( {12,3 - 0,3} \right) - \left( {5,48 + 4,52} \right)\)

\( = 12 - 10\)

\( = 2\).

d) \(\frac{4}{9}.\frac{{ - 7}}{{26}} + \frac{{45}}{{ - 26}}.\frac{4}{9} + \frac{1}{3}\)

\( = \frac{4}{9}.\frac{{ - 7}}{{26}} - \frac{{45}}{{26}}.\frac{4}{9} + \frac{1}{3}\)

\( = \frac{4}{9}.\left( {\frac{{ - 7}}{{26}} - \frac{{45}}{{26}}} \right) + \frac{1}{3}\)

\( = \frac{4}{9}.\frac{{ - 52}}{{26}} + \frac{1}{3}\)

\( = \frac{4}{9}.\left( { - 2} \right) + \frac{1}{3}\)

\( = \frac{{ - 8}}{9} + \frac{3}{9} = \frac{{ - 5}}{9}\).