cách 1 :
\(\frac{3}{5}\chi\frac{7}{9}+\frac{3}{5}\chi\frac{2}{9}\)
= \(\frac{3}{5}\chi\left(\frac{7}{9}+\frac{2}{9}\right)\)
= \(\frac{3}{5}\chi1\)
= \(\frac{3}{5}\)
cách 2 :
\(\frac{3}{5}\chi\frac{7}{9}+\frac{3}{5}\chi\frac{2}{9}\)
= \(\frac{7}{15}\) + \(\frac{2}{15}\)
= \(\frac{9}{15}=\frac{3}{5}\)
\(C1:\frac{3}{5}.\frac{7}{9}+\frac{3}{5}.\frac{2}{9}\) \(C2:\frac{3}{5}.\frac{7}{9}+\frac{3}{5}.\frac{2}{9}\)
\(=\frac{3}{5}\left(\frac{7}{9}+\frac{2}{9}\right)=\frac{3}{5}.1=\frac{3}{5}\) \(=\frac{7}{15}+\frac{2}{15}=\frac{3}{5}\)
\(C1:\frac{8}{15}:\frac{2}{11}+\frac{7}{15}:\frac{2}{11}\) \(C2:\frac{8}{15}:\frac{2}{11}+\frac{7}{15}:\frac{2}{11}\)
\(=\left(\frac{8}{15}+\frac{7}{15}\right):\frac{2}{11}=1:\frac{2}{11}=\frac{11}{2}\) \(=\frac{44}{15}+\frac{77}{30}=\frac{88}{30}+\frac{77}{30}=\frac{11}{2}\)
a)3/15*7/9+3/5*2/9
=(3/15*7/9)+(3/5*2/9)
=21/45+6/45
=27/45=3/5
c2:
=3/5*(7/9+2/9)
=3/5*9/9
=3/5
b)
=(8/15:2/11)+(7/15:2/11)
=44/15+77/30
=11/2
c2)
=(8/15+7/15):2/11
=15/15:2/11
=11/2
