Tính (theo mẫu):
Mẫu: \(\displaystyle {4 \over 5} \times {3 \over 7} = {{4 \times 3} \over {5 \times 7}} = {{12} \over {35}}\)
a) \(\displaystyle {4 \over 9} \times {1 \over 3}\) b) \(\displaystyle {1 \over 9} \times {1 \over 2}\) c) \(\displaystyle {1 \over 5} \times {3 \over 8}\)
a) \(\displaystyle {4 \over 9} \times {1 \over 3} = {{4 \times 1} \over {9 \times 3}} = {4 \over {27}}\)
b) \(\displaystyle {1 \over 9} \times {1 \over 2} = {{1 \times 1} \over {9 \times 2}} = {1 \over {18}}\)
c) \(\displaystyle {1 \over 5} \times {3 \over 8} = {{1 \times 3} \over {5 \times 8}} = {3 \over {40}}\)
-- Mod Toán lớp 4