tính bằng cách thuận tiện nhất
a,3/5*7/9+11/9*3/5-3/10
b,14/13chia 1/2+3/13*2-2*7/13
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\(\dfrac{8}{13}+\dfrac{4}{9}+\dfrac{1}{3}+\dfrac{5}{13}+3\)
\(=1+\dfrac{7}{9}+3\)
\(=4+\dfrac{7}{9}=\dfrac{43}{9}\)
Bài 4:
a: \(=\dfrac{11}{21}\left(\dfrac{7}{4}+\dfrac{5}{4}\right)=\dfrac{11}{21}\cdot3=\dfrac{11}{7}\)
b: \(=\dfrac{6}{13}\left(\dfrac{23}{14}-\dfrac{9}{14}\right)=\dfrac{6}{13}\)
Bài 4:
a: =11/21(7/4+5/4)=11/21x3=11/7
b: =6/13(23/14-9/14)=6/13
A)\(\frac{3}{5}\times\frac{7}{9}+\frac{11}{9}\times\frac{3}{5}-\frac{3}{10}\\ =\frac{3}{5}\times\left(\frac{7}{9}+\frac{11}{9}\right)-\frac{3}{10}\\ =\frac{3}{5}\times\frac{18}{9}-\frac{3}{10}=\frac{3\times2}{5}-\frac{3}{10}\)
\(=\frac{6}{5}-\frac{3}{10}=\frac{12}{10}-\frac{3}{10}=\frac{9}{10}\)
`a: =(7/3-4/3)+11/5=16/5`
`b: =(18/13-5/13)+55/46=1+55/46=101/46`
`c: =27/25-4/9-2/25+5/9=(27/25-2/25)+(5/9-4/9)=1+1/9=10/9`
A =\(\frac{2}{5}\times\frac{4}{7}+\frac{3}{5}\times\frac{4}{7}\) B = \(\frac{17}{13}\times\frac{12}{17}-\frac{4}{13}\times\frac{12}{17}\) C = \(\frac{9}{14}:\frac{6}{7}+\frac{5}{14}:\frac{6}{7}\) D =\(\frac{9}{12}:\frac{7}{9}\times\frac{12}{19}\)
= \(\frac{4}{7}\times\left(\frac{2}{5}+\frac{3}{5}\right)\) =\(\left(\frac{17}{13}-\frac{4}{13}\right)\times\frac{12}{17}\) = \((\frac{9}{14}+\frac{5}{14}):\frac{6}{7}\) = \(\frac{9}{12}\times\frac{9}{7}\times\frac{12}{19}\)
=\(\frac{4}{7}\times1\) = \(1\times\frac{12}{17}\) = \(1:\frac{6}{7}\) = \(\frac{9\times9\times12}{12\times7\times19}\)
=\(\frac{4}{7}\) = \(\frac{12}{17}\) =\(\frac{7}{6}\) = \(\frac{9\times9}{7\times19}=\frac{81}{133}\)
\(\dfrac{2}{3}+\dfrac{7}{13}-\dfrac{17}{9}+\dfrac{19}{13}-\dfrac{1}{9}+\dfrac{7}{3}\)
\(=\left(\dfrac{2}{3}+\dfrac{7}{3}\right)+\left(\dfrac{7}{13}+\dfrac{19}{13}\right)-\left(\dfrac{17}{9}+\dfrac{1}{9}\right)\)
\(=\dfrac{9}{3}+\dfrac{26}{13}-\dfrac{18}{9}\)
\(=3+2-2\)
\(=3\)
a,3/5*7/9+11/9*3/5-3/10=3/5*(7/9+11/9)-3/10
=3/5*18/9-3/10
=3/5*2-3/10
=6/5-3/10
=12/10-3/10
=9/10
b,14/13:1/2+3/13*2-2*7/13=14/13*2+3/13*2-2*7/13
=2*(14/13+3/13-7/13)
=2*10/13
=20/13
a/ ( 7/9 + 11/9 ) x 3/5 - 3/10
= 2 x 3/5 - 3/10
= 6/5 - 3/10
= 9/10
b/ 14/13 : 1/2 + 3/13 x 2 - 2 x 7/13
14/13 x 2/1 + 3/13 x 2 - 2 x 7/13
2 x ( 14/13 + 3/13 - 7/13 )
2 x 10/13
20/13