Tính :
a) \(\displaystyle {2 \over 3} \times {1 \over 6} \times {9 \over 11}\)
b) \(\displaystyle {{2 \times 3 \times 4} \over {2 \times 3 \times 4 \times 5}}\)
a) \(\displaystyle {2 \over 3} \times {1 \over 6} \times {9 \over 11} = \dfrac{2\times1 \times 9}{3\times 6 \times 11}\)\(\displaystyle = \dfrac{\not{2} \times 1 \times \not{3}\times \not{3} }{ \not{3}\times \times \not{2}\times \not{3} \times 11}={1 \over 11} \)
b) \(\displaystyle {{2 \times 3 \times 4} \over {2 \times 3 \times 4 \times 5}} \)\(\displaystyle = {{\not{2} \times \not{3} \times \not{4}} \over {\not{2} \times \not{3} \times \not{4} \times 5}}\)\(=\dfrac{1}{5}\)
-- Mod Toán lớp 4