Question

tính bằng cách thuận tiện
 
\(\dfrac{3}{4}\)x\(\dfrac{1}{5}\)x\(\dfrac{8}{9}\)                                              \(\dfrac{2}{3}\)x\(\dfrac{10}{21}\)x\(\dfrac{3}{2}\)                     

                          

Answer 1

\(a,=\left(\dfrac{3}{4}.\dfrac{8}{9}\right).\dfrac{1}{5}=\dfrac{2}{3}.\dfrac{1}{5}=\dfrac{2}{15}\\ b,=\left(\dfrac{2}{3}.\dfrac{3}{2}\right).\dfrac{10}{21}\\ =1.\dfrac{10}{21}\\ =\dfrac{10}{21}\)

Answer 2

\(\dfrac{3}{4}\times\dfrac{1}{5}\times\dfrac{8}{9}=1\times\dfrac{1}{5}\times1=\dfrac{1}{5}\)

\(\dfrac{2}{3}\times\dfrac{10}{21}\times\dfrac{3}{2}=\left(\dfrac{2}{3}\times\dfrac{3}{2}\right)\times\dfrac{10}{21}=\dfrac{6}{6}\times\dfrac{10}{21}=1\times\dfrac{10}{21}=\dfrac{10}{21}\)