Bài 5:
a) \(0,24\cdot-\dfrac{15}{4}=\dfrac{6}{25}\cdot-\dfrac{15}{4}=\dfrac{6\cdot-15}{25\cdot4}=-\dfrac{90}{100}=-\dfrac{9}{10}\)
b) \(4,5\cdot\dfrac{-4}{9}=\dfrac{9}{2}\cdot\dfrac{-4}{9}=\dfrac{9\cdot-4}{2\cdot9}=-\dfrac{4}{2}=-2\)
c) \(3,5\cdot-1\dfrac{2}{5}=\dfrac{7}{2}\cdot\dfrac{-7}{5}=\dfrac{7\cdot-7}{2\cdot5}=-\dfrac{49}{10}\)
Bài 6:
a) \(1\dfrac{1}{17}\cdot\left(-2\dfrac{1}{8}\right)=\dfrac{18}{17}\cdot\dfrac{-17}{8}=\dfrac{18\cdot-17}{17\cdot8}=\dfrac{-18}{8}=-\dfrac{9}{4}\)
b) \(\left(-2\dfrac{1}{3}\right)\cdot1\dfrac{1}{14}=-\dfrac{7}{3}\cdot\dfrac{15}{14}=\dfrac{-7\cdot15}{3\cdot14}=-\dfrac{5}{2}\)
c) \(1,25\cdot\left(-3\dfrac{3}{8}\right)=\dfrac{5}{4}\cdot-\dfrac{27}{8}=\dfrac{5\cdot-27}{4\cdot8}=-\dfrac{135}{32}\)
`@` `\text {Ans}`
`\downarrow`
`5,`
`a)`
\(0,24\cdot\dfrac{-15}{4}\)
`= (0,24*(-15))/4`
`= (-3,6)/4 = -9/10`
`b)`
\(4,5\cdot\left(-\dfrac{4}{9}\right)\)
`= (4,5*(-4))/9`
`= -18/9 = -2`
`c)`
\(3,5\cdot\left(-1\dfrac{2}{5}\right)\)
`= 3,5*(-7/5)`
`= (3,5*(-7))/5`
`=(-24,5)/5 = -49/10`
`6,`
`a)`
\(1\dfrac{1}{17}\cdot\left(-2\dfrac{1}{8}\right)\)
`= 18/17 * (-17/8)`
`= -18/8 = -9/4`
`b)`
\(\left(-2\dfrac{1}{3}\right)\cdot1\dfrac{1}{14}\)
`= -7/3*15/14`
`= -1*5/2`
`= -5/2`
`c)`
\(1,25\cdot\left(-3\dfrac{3}{8}\right)\)
`= 1,25*(-27/8)`
`= (1,25*(-27))/8`
`= (-33,75)/8 = -135/32`