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b)\(\left(\dfrac{13}{21}\times\dfrac{7}{8}-\dfrac{12}{21}\times\dfrac{7}{8}\right)\times12\)
=\(\left(\dfrac{7}{8}\times\left(\dfrac{13}{21}-\dfrac{12}{21}\right)\right)\times12\)
=\(\left(\dfrac{7}{8}\times\dfrac{1}{21}\right)\times12\)
=\(\dfrac{7}{16}\)
c)\(\dfrac{7}{11}+\dfrac{3}{4}+\dfrac{4}{11}+\dfrac{8}{17}+\dfrac{1}{4}+\dfrac{18}{34}\)
= \(\left(\dfrac{7}{11}+\dfrac{4}{11}\right)+\left(\dfrac{3}{4}+\dfrac{1}{4}\right)+\dfrac{8}{17}+\dfrac{9}{17}\)
= 1 + 1 + \(\left(\dfrac{8}{17}+\dfrac{9}{17}\right)\)
= 2 + 1
= 3
Ta có ; \(\frac{3}{7}\times\frac{4}{11}+\frac{3}{7}\times\frac{5}{11}+\frac{1}{2}\)
\(=\frac{3}{7}\times\left(\frac{4}{11}+\frac{5}{11}\right)+\frac{1}{2}\)
\(=\frac{3}{7}\times\frac{9}{11}+\frac{1}{2}\)
\(=\frac{27}{77}+\frac{1}{2}\)
\(=\frac{131}{154}\)
C1 : \(\frac{7}{11}\):\(\frac{3}{5}\)+\(\frac{4}{11}\):\(\frac{3}{5}\)
=\(\frac{7}{11}\)x\(\frac{5}{3}\)+\(\frac{4}{11}\)x\(\frac{5}{3}\)
=\(\frac{35}{33}\)+\(\frac{20}{33}\)
=\(\frac{55}{33}\)=\(\frac{5}{3}\)
C2: \(\frac{7}{11}\):\(\frac{3}{5}\)+\(\frac{4}{11}\):\(\frac{3}{5}\)
= \(\frac{3}{5}\)x (\(\frac{7}{11}\)+\(\frac{4}{11}\))
=\(\frac{3}{5}\)x 1= \(\frac{3}{5}\)
\(C1:\frac{7}{11}:\frac{3}{5}+\frac{4}{11}:\frac{3}{5}\)
\(=\frac{7}{11}x\frac{5}{3}+\frac{4}{11}x\frac{5}{3}\)
\(=\frac{35}{33}+\frac{20}{33}\)
\(=\frac{55}{33}=\frac{5}{3}\)
\(C2:\frac{7}{11}:\frac{3}{5}+\frac{4}{11}:\frac{3}{5}\)
\(=\frac{7}{11}x\frac{5}{3}+\frac{4}{11}x\frac{5}{3}\)
\(=\frac{5}{3}x\left(\frac{7}{11}+\frac{4}{11}\right)\)
\(=\frac{5}{3}x1=\frac{5}{3}\)
a= (\(\frac{2}{5}\)+\(\frac{2}{9}\)+\(\frac{2}{11}\)\(\times\)\(\frac{5}{7}\)\(+\frac{7}{9}\)\(+\frac{7}{11}\)\()\)
\(\frac{7}{11}+\frac{3}{4}+\frac{4}{11}+\frac{1}{4}\)
= \(\left(\frac{7}{11}+\frac{4}{11}\right)+\left(\frac{3}{4}+\frac{1}{4}\right)\)
= \(\frac{11}{11}+\frac{4}{4}\)
= 1 + 1
= 2
\(3\frac{5}{11}+\frac{4}{17}-\frac{5}{11}-\frac{3}{17}\)
\(=\left(3\frac{5}{11}-\frac{5}{11}\right)+\left(\frac{4}{17}-\frac{3}{17}\right)\)
\(=3+\frac{1}{17}\)
\(=\frac{51}{17}+\frac{1}{17}\)
\(=\frac{52}{17}\)
Chúc bạn học tốt !!!
a, 6/9+5/7+1/3=2/3+5/7+1/3=5/7+1=12/7
b, 17/7+6/5-20/14=17/7+6/5-10/7=6/5+1=11/5
c,2/5x1/4+3/4x2/5=2/5x(1/4+3/4)=2/5x1=2/5
d, 6/11:4/6+5/11:2/3=6/11:2/3+5/11:2/3=(6/11+5/11):2/3=3/2
nha