Bài 2: Tính : a) \(\frac{2 × 3 × 4}{3 × 4 ×5}\) ; b) \(\frac{2 }{3 }\) x \(\frac{3}{4 }\) x \(\frac{
Bài 2: Tính:
a) \(\frac{2 × 3 × 4}{3 × 4 ×5}\) ; b) \(\frac{2 }{3 }\) x \(\frac{3}{4 }\) x \(\frac{4}{5 }\) : \(\frac{1}{5 }\) ;
c) \(\frac{1 ×2 ×3× 4}{5× 6× 7× 8 }\) ; d) \(\frac{2}{5 }\) x \(\frac{3}{4 }\) x \(\frac{5}{6 }\) : \(\frac{3}{4 }\) .
Lời Giải:
Bài 2:
a) \(\frac{2 × 3 × 4}{3 × 4 × 5}\) = \(\frac{2}{5}\) ;
b) \(\frac{2 }{3 }\) x \(\frac{3}{4 }\) x \(\frac{4}{5 }\) : \(\frac{1}{5 }\) = \(\frac{2}{5}\) : \(\frac{1}{5}\) = \(\frac{2}{5}\) x \(\frac{5}{1}\) = 2
hoặc \(\frac{2 }{3 }\) x \(\frac{3}{4 }\) x \(\frac{4}{5 }\) : \(\frac{1}{5 }\) = \(\frac{2 }{3 }\) x \(\frac{3}{4 }\) x \(\frac{4}{5 }\) x \(\frac{5}{1}\) = 2.
c) \(\frac{1 ×2 × 3 × 4}{5 × 6× 7 × 8 }\) = \(\frac{1× 2 × 3 × 4}{5 × 2 × 3 × 7 × 2 × 4}\) = \(\frac{1 }{70}\)
d) \(\frac{2}{5 }\) x \(\frac{3}{4 }\) x \(\frac{5}{6 }\) : \(\frac{3}{4 }\) = \(\frac{1 }{4}\) : \(\frac{3}{4 }\) = \(\frac{1 }{4}\) x \(\frac{4}{3}\) = \(\frac{1}{3}\)
Hoặc \(\frac{2}{5 }\) x \(\frac{3}{4 }\) x \(\frac{5}{6 }\) : \(\frac{3}{4 }\) = \(\frac{2}{5 }\) x \(\frac{3}{4 }\) x \(\frac{5}{6 }\) x \(\frac{4}{3}\) = \(\frac{2}{6}\) = \(\frac{1}{3}\)