Bài tập 2 trang 112 VBT Toán 4 tập 2

a) \(\displaystyle \frac{4}{7} + \frac{5}{{14}} - \frac{1}{2} = \frac{{8 }}{{14}}  + \frac{5}{{14}}- \frac{1}{2}\)\(\displaystyle = \frac{{13}}{{14}} - \frac{1}{2} = \frac{{13 }}{{14}} - \frac{7}{14}= \frac{6}{{14}} = \frac{3}{7}\)

b) \(\displaystyle \frac{9}{{17}} + \frac{9}{{34}} \times \frac{2}{3} = \frac{9}{{17}} + \frac{{9 \times 2}}{{34 \times 3}}\)\(\displaystyle = \frac{9}{{17}} + \frac{3}{{17}} = \frac{{9 + 3}}{{17}} = \frac{{12}}{{17}}\) 

c) \(\displaystyle \frac{5}{9} \times \frac{3}{{10}}:\frac{7}{{12}} = \frac{{5 \times 3}}{{9 \times 10}}:\frac{7}{{12}}\)\(\displaystyle = \frac{1}{6} \times \frac{{12}}{7} = \frac{{1 \times 12}}{{6 \times 7}} = \frac{2}{7}\)

-- Mod Toán lớp 4 HỌC247