Bài 1: Trang 167 - sgk toán lớp 4
Tính:
$\frac{2}{7} + \frac{4}{7}$ $\frac{6}{7} - \frac{2}{7}$ $\frac{6}{7} - \frac{4}{7}$ $\frac{4}{7} + \frac{2}{7}$
$\frac{1}{3} + \frac{5}{12}$ $\frac{9}{12} - \frac{1}{3}$ $\frac{9}{12} - \frac{5}{12}$ $\frac{5}{12} + \frac{1}{3}$
Bài Làm:
$\frac{2}{7} + \frac{4}{7}= \frac{6}{7}$
$\frac{6}{7} - \frac{2}{7}= \frac{5}{7}$
$\frac{6}{7} - \frac{4}{7}= \frac{2}{7}$
$\frac{4}{7} + \frac{2}{7}= \frac{6}{7}$
$\frac{1}{3} + \frac{5}{12}= \frac{4}{12}+ \frac{5}{12}=\frac{9}{12}$
$\frac{9}{12} - \frac{1}{3}= \frac{9}{12} - \frac{4}{12}=\frac{5}{12}$
$\frac{9}{12} - \frac{5}{12}= \frac{4}{12}$
$\frac{5}{12} + \frac{1}{3}= \frac{5}{12}+ \frac{4}{12}=\frac{9}{12}$
