Câu 4: Trang 53 sách VNEN toán 4
Tính:
$\frac{4}{7}\times \frac{5}{4}$; $\frac{6}{5}\times \frac{5}{7}$; $\frac{11}{3}\times \frac{3}{11}$
Bài Làm:
$\frac{4}{7}\times \frac{5}{4}=\frac{4\times 5}{7\times 4}=\frac{20}{28}$
$\frac{6}{5}\times \frac{5}{7}=\frac{6\times 5}{5\times 7}=\frac{30}{35}$
$\frac{11}{3}\times \frac{3}{11}=\frac{11\times 3}{3\times 11}=\frac{33}{33}$