\(\dfrac{2}{5};\dfrac{3}{7};\dfrac{1}{2}\) Mẫu chung: 5 x 7 x 2 = 70
Quy đồng:
\(\dfrac{2}{5}=\dfrac{2\times14}{5\times14}=\dfrac{28}{70}\);
\(\dfrac{3}{7}=\dfrac{3\times10}{7\times10}=\dfrac{30}{70}\);
\(\dfrac{1}{2}=\dfrac{1\times35}{2\times35}=\dfrac{35}{70}\)
Mẫu số chung là 70:
\(\dfrac{2}{5}\) = \(\dfrac{28}{70}\) \(\dfrac{3}{7}\) = \(\dfrac{30}{70}\) \(\dfrac{1}{2}\) = \(\dfrac{35}{70}\)