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\(\dfrac{7}{5}+\dfrac{8}{5}+\dfrac{7}{2}+\dfrac{1}{2}+\dfrac{12}{13}+\dfrac{27}{13}=\dfrac{15}{5}+\dfrac{8}{2}+\dfrac{39}{13}=3+4+3=10\)
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a,\(\frac{1}{5}\times\frac{2}{9}\div\frac{1}{15}\)
\(=\frac{1}{5}\times\frac{2}{9}\times15\)
\(=\left(\frac{1}{5}\times15\right)\times\frac{2}{9}\)
\(=3\times\frac{2}{9}\)
\(=\frac{2}{3}\)
b\(\frac{4}{15}\times\frac{7}{15}\times\frac{5}{4}\)
\(=\left(\frac{4}{15}\times\frac{5}{4}\right)\times\frac{7}{15}\)
\(=\frac{1}{3}\times\frac{7}{15}\)
\(=\frac{7}{45}\)
c,\(\frac{21}{23}\times\frac{5}{11}\times\frac{44}{?}\)
d,\(26\times\frac{13}{42}\div13\)
\(=\left(26\div13\right)\times\frac{13}{42}\)
\(=2\times\frac{13}{42}\)
\(=\frac{13}{21}\)
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a) \(\frac{3}{5}+\frac{6}{11}+\frac{7}{13}+\frac{2}{5}+\frac{16}{11}+\frac{19}{13}\)
\(=\left(\frac{3}{5}+\frac{2}{5}\right)+\left(\frac{6}{11}+\frac{16}{11}\right)+\left(\frac{7}{13}+\frac{19}{13}\right)\)
\(=1+2+2=5\)
b) \(\frac{1995}{1997}x\frac{1990}{1993}x\frac{1997}{1994}x\frac{1993}{1995}x\frac{997}{995}=\frac{1995x1990x1997x1993x997}{1997x1993x1994x1995x995}=\frac{1990x997}{1994x995}=\frac{995x2x997}{997x2x995}=1\)
a) =(3/5+2/5)+(6/11+16/11)+(19/13+7/13)
=5/5+22/11+26/13
=1+2+3
=6
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\(\frac{13}{90}\)+ \(\frac{1}{4}\)+ \(\frac{77}{90}\)
= \(\left(\frac{13}{90}+\frac{77}{90}\right)+\frac{1}{4}\)
= 1 + \(\frac{1}{4}\)
= \(\frac{5}{4}\)
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`16/27xx13/29+16/27xx14/29`
`=16/27xx(13/29+14/29)`
`=16/27xx27/29`
`=16/29`
`48/49+15/39-18/49+15/39`
`=(48/49-18/49)+(15/39+15/39)`
`=30/49+30/39`
`=880/637`
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nhóm các số có cùng mẫu với nhau rồi cộng ra
=\(\dfrac{13}{22}\cdot4+\dfrac{4}{22}\cdot4=\dfrac{4}{22}\left(13+4\right)=\dfrac{4}{22}\cdot17=\dfrac{2}{11}\cdot17=\dfrac{34}{11}\)