Thực hiện phép tính (tính nhanh nếu có thể)
a) \(\left( {5 + \dfrac{1}{5} - \dfrac{2}{9}} \right) - \left( {2 - \dfrac{1}{{23}} - 2\dfrac{3}{{35}} + \dfrac{5}{6}} \right) - \left( {8 + \dfrac{2}{7} - \dfrac{1}{{18}}} \right)\)
b) \( - \dfrac{5}{7} - \left( { - \dfrac{5}{{67}}} \right) + \dfrac{{13}}{{30}} + \dfrac{1}{2} + \left( { - 1\dfrac{5}{6}} \right) + 1\dfrac{3}{{14}} - \left( { - \dfrac{2}{5}} \right)\)
c) \(13\dfrac{9}{{11}} - 25\% + 6\dfrac{2}{{11}} + 45\% \)
d)\(\dfrac{3}{{25}} - \left( {6\% + 12\% } \right) + \dfrac{2}{3} + 83\% - \dfrac{5}{{12}}\)
Câu 573463: Thực hiện phép tính (tính nhanh nếu có thể)
a) \(\left( {5 + \dfrac{1}{5} - \dfrac{2}{9}} \right) - \left( {2 - \dfrac{1}{{23}} - 2\dfrac{3}{{35}} + \dfrac{5}{6}} \right) - \left( {8 + \dfrac{2}{7} - \dfrac{1}{{18}}} \right)\)
b) \( - \dfrac{5}{7} - \left( { - \dfrac{5}{{67}}} \right) + \dfrac{{13}}{{30}} + \dfrac{1}{2} + \left( { - 1\dfrac{5}{6}} \right) + 1\dfrac{3}{{14}} - \left( { - \dfrac{2}{5}} \right)\)
c) \(13\dfrac{9}{{11}} - 25\% + 6\dfrac{2}{{11}} + 45\% \)
d)\(\dfrac{3}{{25}} - \left( {6\% + 12\% } \right) + \dfrac{2}{3} + 83\% - \dfrac{5}{{12}}\)
+ Quy tắc cộng, trừ số hữu tỉ:
Ta có thể cộng, trừ hai số hữu tỉ \(x,y\) bằng cách viết chúng dưới dạng hai phân số có cùng một mẫu dương rồi áp dụng quy tắc cộng, trừ phân số:
Với \(x = \dfrac{a}{m};y = \dfrac{b}{m}\left( {a,b,m \in \mathbb{Z},m > 0} \right)\): \(x + y = \dfrac{a}{m} + \dfrac{b}{m} = \dfrac{{a + b}}{m}\)
Với \(x = \dfrac{a}{m};y = \dfrac{b}{m}\left( {a,b,m \in \mathbb{Z},m > 0} \right)\): \(x - y = \dfrac{a}{m} - \dfrac{b}{m} = \dfrac{{a - b}}{m}\)
+ Ta có: \( - \left( { - a} \right) = a\)
-
Giải chi tiết:
a) \(\left( {5 + \dfrac{1}{5} - \dfrac{2}{9}} \right) - \left( {2 - \dfrac{1}{{23}} - 2\dfrac{3}{{35}} + \dfrac{5}{6}} \right) - \left( {8 + \dfrac{2}{7} - \dfrac{1}{{18}}} \right)\)
\(\begin{array}{l} = 5 + \dfrac{1}{5} - \dfrac{2}{9} - 2 + \dfrac{1}{{23}} + 2\dfrac{3}{{35}} - \dfrac{5}{6} - 8 - \dfrac{2}{7} + \dfrac{1}{{18}}\\ = \left( {5 - 2 - 8} \right) + \left( {\dfrac{1}{5} + 2\dfrac{3}{{35}} - \dfrac{2}{7}} \right) + \left( { - \dfrac{2}{9} - \dfrac{5}{6} + \dfrac{1}{{18}}} \right) + \dfrac{1}{{23}}\\ = \left( { - 5} \right) + \left( {\dfrac{7}{{35}} + \dfrac{{73}}{{35}} - \dfrac{{10}}{{35}}} \right) + \left( { - \dfrac{4}{{18}} - \dfrac{{15}}{{18}} + \dfrac{1}{{18}}} \right) + \dfrac{1}{{23}}\\ = \left( { - 5} \right) + 2 + \left( { - 1} \right) + \dfrac{1}{{23}}\\ = - 4 + \dfrac{1}{{23}}\\ = \dfrac{{ - 91}}{{23}}\end{array}\)
b)\( - \dfrac{5}{7} - \left( { - \dfrac{5}{{67}}} \right) + \dfrac{{13}}{{30}} + \dfrac{1}{2} + \left( { - 1\dfrac{5}{6}} \right) + 1\dfrac{3}{{14}} - \left( { - \dfrac{2}{5}} \right)\)
\(\begin{array}{l} = - \dfrac{5}{7} + \dfrac{5}{{67}} + \dfrac{{13}}{{30}} + \dfrac{1}{2} - 1\dfrac{5}{6} + 1\dfrac{3}{{14}} + \dfrac{2}{5}\\ = \left( { - \dfrac{5}{7} + \dfrac{1}{2} + 1\dfrac{3}{{14}}} \right) + \left( {\dfrac{{13}}{{30}} - 1\dfrac{5}{6} + \dfrac{2}{5}} \right) + \dfrac{5}{{65}}\\ = \left( { - \dfrac{{10}}{{14}} + \dfrac{7}{{14}} + \dfrac{{17}}{{14}}} \right) + \left( {\dfrac{{13}}{{30}} - \dfrac{{55}}{{30}} + \dfrac{{12}}{{30}}} \right) + \dfrac{5}{{67}}\\ = 1 + \left( { - 1} \right) + \dfrac{5}{{67}}\\ = \dfrac{5}{{67}}\end{array}\)
c)\(13\dfrac{9}{{11}} - 25\% + 6\dfrac{2}{{11}} + 45\% \)
\(\begin{array}{l} = \left( {13\dfrac{9}{{11}} + 6\dfrac{2}{{11}}} \right) + \left( { - 25\% + 45\% } \right)\\ = \left( {\dfrac{{152}}{{11}} + \dfrac{{68}}{{11}}} \right) + 20\% \\ = 20 + 0,2\\ = 20,2\end{array}\)
d)\(\dfrac{3}{{25}} - \left( {6\% + 12\% } \right) + \dfrac{2}{3} + 83\% - \dfrac{5}{{12}}\)
\(\begin{array}{l} = \dfrac{3}{{25}} - 18\% + 83\% + \dfrac{8}{{12}} - \dfrac{5}{{12}}\\ = \dfrac{3}{{25}} + 65\% + \dfrac{1}{4}\\ = \dfrac{{12}}{{100}} + \dfrac{{65}}{{100}} + \dfrac{{25}}{{100}}\\ = \dfrac{{102}}{{100}} = \dfrac{{51}}{{50}}\end{array}\)
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