\(\frac{3}{5}\times\frac{7}{21}+\frac{7}{21}\times\frac{2}{5}=\frac{7}{21}\times\left(\frac{3}{5}+\frac{2}{5}\right)=\frac{1}{3}\times\left(\frac{3}{5}+\frac{2}{5}\right)=\frac{1}{3}\times1=\frac{1}{3}\)

   Học tốt !

\(\frac{3}{5}\cdot\frac{7}{21}+\frac{7}{21}+\frac{2}{5}\)

\(=\frac{7}{21}\cdot(\frac{3}{5}+\frac{2}{5})\)

\(=\frac{7}{21}\cdot1=\frac{7}{21}=\frac{1}{3}\)

C1  \(\frac{3}{5}.\frac{7}{21}+\frac{7}{21}.\frac{2}{5}\)

\(=\frac{7}{21}\left(\frac{3}{5}+\frac{2}{5}\right)\)

\(=\frac{7}{21}.1\)

\(=\frac{7}{21}=\frac{1}{3}\)

C2   \(\frac{3}{5}.\frac{7}{21}+\frac{7}{21}.\frac{2}{5}\)

\(=\frac{3.7}{5.21}+\frac{7.2}{21.5}\)

\(=\frac{21}{105}+\frac{14}{105}\)

\(=\frac{35}{105}\)

\(=\frac{7}{21}=\frac{1}{3}\)

\(\frac{1}{1.2}+\frac{3}{2.5}+\frac{7}{5.12}+\frac{13}{12.25}+\frac{21}{25.46}\)

\(=1-\frac{1}{2}+\frac{1}{2}-\frac{1}{5}+\frac{1}{5}-\frac{1}{12}+\frac{1}{12}-\frac{1}{25}+\frac{1}{25}-\frac{1}{46}\)

\(=1-\frac{1}{46}\)

\(=\frac{45}{46}\)

a) \(\frac{1}{4}\) 

b) \(\frac{2}{7}\)

c) \(\frac{2}{3}\)

à còn phần d là \(\frac{1}{7}\)

1/4

2/7

2/3

2/3 *  10/21 * 3/2 = (2/3 * 3/2) * 10/21 = 1 * 10/21 = 10/21

22/5 * 12 * 5/12 = 22/5 * (12 * 5/12) = 22/5 * 5 =22

7/2 * 28/81 * 2/7= (7/2 * 2/7) * 28/81 = 1 * 28/81 =28/81

5/17 * 21/4 * 47/15 * 0 = 0

~Study well~

#Seok_Jin#

ARE YOU KOREAN ???

\(\frac{2}{3}\times\frac{10}{21}\times\frac{3}{2}\)

\(=\left(\frac{2}{3}\times\frac{3}{2}\right)\times\frac{10}{21}\)

\(=\left(\frac{1}{1}\times\frac{1}{1}\right)\times\frac{10}{21}\)

\(=1\times\frac{10}{21}\)

\(=\frac{10}{21}\)