a/ \(\dfrac{2}{3}.\dfrac{3}{4}.\dfrac{4}{5}=\dfrac{2.3.2.2}{3.2.2.5}=\dfrac{2}{5}\)
b/ \(\dfrac{1}{2}:\dfrac{3}{4}:\dfrac{5}{6}=\dfrac{2}{1}.\dfrac{4}{3}.\dfrac{6}{5}=\dfrac{2.2.2.2.3}{1.3.5}=\dfrac{16}{5}\)
a/\(\dfrac{2}{5}=0,4\)
b/\(\dfrac{16}{5}=3,2\)
Thiếu nên mk bổ sung thêm bởi vì lúc dầu mk chưa đọc kĩ đề