a: \(\dfrac{7}{13}\cdot\dfrac{5}{14}\cdot\dfrac{39}{15}=\dfrac{39}{13}\cdot\dfrac{5}{15}\cdot\dfrac{1}{2}=\dfrac{1}{2}\)
b: \(=\dfrac{15}{17}\left(\dfrac{9}{5}+\dfrac{8}{5}\right)=\dfrac{15}{17}\cdot\dfrac{17}{5}=3\)
c: \(=\dfrac{1}{2}\left(2+\dfrac{3}{7}-\dfrac{3}{7}\right)+\dfrac{1}{3}=1+\dfrac{1}{3}=\dfrac{4}{3}\)
d) \(100\%+28,4\%-36,7\%\)
\(=1+\dfrac{71}{250}-\dfrac{367}{1000}\)
\(=\dfrac{1000}{1000}+\dfrac{284}{1000}-\dfrac{367}{1000}\)
\(=\dfrac{917}{1000}\)
Dấu ''.'' là dấu nhân đó bn
ở câu `c)` bn nên viết rõ là dấy `,` và lên lớp `6` dấu `.` có tác dụng là nhân nhé `^^`
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`a) 7/13 xx 5/14 xx 39/15 = (7 xx 5 xx 39)/(13 xx 14 xx 15) = 1365/2730 = 1/2`
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`b)9/5 : 17/15 + 8/5 : 17/15`
`= 9/5 xx 15/17 + 8/5 xx 15/17`
`= (9/5 + 8/5) xx 15/17`
`= 17/5 xx 15/17`
`= 1`
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`c) 2 3/7 xx 1/2 - 1/2 xx 3/7 + 1/3`
`= 17/7 xx 1/2 - 1/2 xx 3/7 + 1/3`
`= (17/7 - 3/7) xx 1/2 + 1/3`
`= 2 xx 1/2 + 1/3`
`= 1 + 1/3`
`= 4/3`
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`100% + 28,4% - 36,7%`
`= 1 + 71/250 - 367/1000`
`= 321/250 - 367/1000`
`= 917/1000`
