Question

Tính nhanh phân số sau : (1+1/2) x (1+1/3) x (1+1/4) x (1+1/5) x (1+1/6)

Answer 1

\(\left(1+\dfrac{1}{2}\right)\times\left(1+\dfrac{1}{3}\right)\times\left(1+\dfrac{1}{4}\right)\times\left(1+\dfrac{1}{5}\right)\times\left(1+\dfrac{1}{6}\right)\)

\(=\dfrac{3}{2}\times\dfrac{4}{3}\times\dfrac{5}{4}\times\dfrac{6}{5}\times\dfrac{7}{6}\)

\(=\dfrac{3\times4\times5\times6\times7}{2\times3\times4\times5\times6}=\dfrac{7}{2}\)