Question

Rút gọn rồi tính:

a) \(\dfrac{3}{9}\times\dfrac{5}{4}\)                        b) \(\dfrac{10}{15}\times\dfrac{3}{5}\)                      c) \(\dfrac{5}{8}\times\dfrac{4}{12}\)                      d) \(\dfrac{9}{27}\times\dfrac{3}{21}\)

Answer 1

a: \(\dfrac{3}{9}\times\dfrac{5}{4}=\dfrac{5}{4}\times\dfrac{1}{3}=\dfrac{5\times1}{4\times3}=\dfrac{5}{12}\)

b: \(\dfrac{10}{15}\times\dfrac{3}{5}=\dfrac{3}{5}\times\dfrac{2}{3}=\dfrac{3\times2}{5\times3}=\dfrac{2}{5}\)

c: \(\dfrac{5}{8}\times\dfrac{4}{12}=\dfrac{5}{8}\times\dfrac{1}{3}=\dfrac{5}{3\times8}=\dfrac{5}{24}\)

d: \(\dfrac{9}{27}\times\dfrac{3}{21}=\dfrac{1}{7}\times\dfrac{1}{3}=\dfrac{1\times1}{7\times3}=\dfrac{1}{21}\)