Câu 4: Trang 62 sách VNEN toán 4
Tính:
$\frac{3}{5}\times \frac{6}{7}$; $\frac{5}{7}\times 12$; $21\times\frac{2}{7}$
Bài Làm:
$\frac{3}{5}\times \frac{6}{7}=\frac{3\times 6}{5\times 7}=\frac{18}{35}$
$\frac{5}{7}\times 12=\frac{5\times 12}{7}=\frac{60}{7}$
$21\times\frac{2}{7}=\frac{21\times 2}{7}=\frac{42}{7}$