Thực hiện phép tính (tính hợp lí nếu có thể): 2/5 - 1/5 . 3/(-4)

a) \(\frac{2}{5} - \frac{1}{5} \cdot \frac{3}{{ - 4}}\)

\( = \frac{2}{5} - \frac{3}{{ - 20}}\)

\( = \frac{8}{{20}} + \frac{3}{{20}}\)

\( = \frac{{11}}{{20}}.\)

b) \[60,7 + 25,5-38,7\]

\[ = \left( {60,7-38,7} \right) + 25,5\]

\[ = 22 + 25,5\]

\( = 47,5.\)

c) \(\frac{2}{{11}}.\frac{{ - 5}}{4} + \frac{{ - 9}}{{11}}.\frac{5}{4} + 1\frac{3}{4}\)

\( = \frac{2}{{11}} \cdot \frac{{ - 5}}{4} + \frac{9}{{11}} \cdot \frac{{ - 5}}{4} + \frac{7}{4}\)

\( = \frac{{ - 5}}{4} \cdot \left( {\frac{2}{{11}} + \frac{9}{{11}}} \right) + \frac{7}{4}\)

\( = \frac{{ - 5}}{4} \cdot \frac{{11}}{{11}} + \frac{7}{4}\)

\( = \frac{{ - 5}}{4} \cdot 1 + \frac{7}{4}\)

\[ = \frac{{ - 5}}{4} + \frac{7}{4}\]

\[ = \frac{2}{4} = \frac{1}{2}.\]

d) \[25\% - 1\frac{1}{2} - {\left( { - \frac{1}{2}} \right)^2} + 0,75:\frac{1}{2}\]

\[ = \frac{1}{4} - \frac{3}{2} - \frac{1}{4} + \frac{3}{4} \cdot 2\]

\[ = \left( {\frac{1}{4} - \frac{1}{4}} \right) - \frac{3}{2} + \frac{3}{2}\]

\[ = 0 + \left( { - \frac{3}{2} + \frac{3}{2}} \right)\]

\[ = 0.\]