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