CÁCH 1:
\(\frac{3}{5}\times\frac{17}{21}+\frac{17}{21}\times\frac{2}{5}=\frac{17}{35}+\frac{34}{105}=\frac{17}{21}\)
CÁCH 2:
\(\frac{3}{5}\times\frac{17}{21}+\frac{17}{21}\times\frac{2}{5}=\frac{17}{21}\times(\frac{3}{5}+\frac{2}{5})=\frac{17}{21}\times1=\frac{17}{21}\)
Cách 1:
\(\frac{3}{5}\times\frac{17}{21}+\frac{17}{21}\times\frac{2}{5}\)
\(=\frac{3\times17}{5\times21}+\frac{17\times2}{21\times5}\)
\(=\frac{17}{5\times7}+\frac{34}{105}\)
\(=\frac{17}{35}+\frac{34}{105}\)
\(=\frac{17\times3}{35\times3}+\frac{34}{105}\)
\(=\frac{51+34}{105}\)
\(=\frac{85}{105}\)
\(=\frac{17}{21}\)
Cách 2:
\(\frac{3}{5}\times\frac{17}{21}+\frac{17}{21}\times\frac{2}{5}\)
\(=\frac{17}{21}\times\left(\frac{3}{5}+\frac{2}{5}\right)\)
\(=\frac{17}{21}\times1\)
\(=\frac{17}{21}\)
