Question

Chuyển các hỗn số sau thành phân số rồi thực hiện phép tính 

\(a,2\dfrac{1}{3}x5\dfrac{1}{4}\)            \(b,3\dfrac{2}{5}x2\dfrac{1}{7}\)         \(c,8\dfrac{1}{6}:2\dfrac{1}{2}\)

 

Answer 1

\(2\dfrac{1}{3}\times5\dfrac{1}{4}=\dfrac{2.3+1}{3}\times\dfrac{5.4+1}{4}=\dfrac{7}{3}\times\dfrac{21}{4}=\dfrac{49}{4}\)

 

\(3\dfrac{2}{5}\times2\dfrac{1}{7}=\dfrac{3.5+2}{5}\times\dfrac{2.7+1}{7}=\dfrac{17}{5}\times\dfrac{15}{7}=\dfrac{51}{7}\)

 

\(8\dfrac{1}{6}:2\dfrac{1}{2}=\dfrac{8.6+1}{6}:\dfrac{2.2+1}{2}=\dfrac{49}{6}:\dfrac{5}{2}=\dfrac{49}{6}\times\dfrac{2}{5}=\dfrac{49}{15}\)

Answer 2

\(2\dfrac{1}{3}x5\dfrac{1}{4}=\dfrac{7}{3}x\dfrac{21}{4}=\dfrac{49}{4}\)

\(3\dfrac{2}{5}x2\dfrac{1}{7}=\dfrac{17}{5}x\dfrac{15}{7}=\dfrac{17x5x3}{5x7}=\dfrac{51}{7}\)

\(8\dfrac{1}{6}:2\dfrac{1}{2}=\dfrac{49}{6}:\dfrac{5}{2}=\dfrac{49}{6}x\dfrac{2}{5}=\dfrac{49x2}{3x2x5}=\dfrac{49}{15}\)