B. Hoạt động ứng dụng
Câu 1: Trang 59 sách VNEN toán 4
Tính:
$\frac{6}{35} : \frac{3}{7}$ $\frac{6}{35} : \frac{2}{5}$
$\frac{1}{20} : \frac{1}{5}$ $\frac{1}{20} : \frac{1}{4}$
Bài Làm:
$\frac{6}{35} : \frac{3}{7} = \frac{6}{35}\times \frac{7}{3}=\frac{6\times 7}{35\times 3}=\frac{42}{105}$
$\frac{6}{35} : \frac{2}{5} = \frac{6}{35}\times \frac{5}{2}=\frac{6\times 5}{35\times 2}=\frac{30}{70}$
$\frac{1}{20} : \frac{1}{5} = \frac{1}{20}\times \frac{5}{1}=\frac{1\times 5}{20\times 1}=\frac{5}{20}$
$\frac{1}{20} : \frac{1}{4} = \frac{1}{20}\times \frac{4}{1}=\frac{1\times 4}{20\times 1}=\frac{4}{20}$