A is 40 % more efficient than B. How much time will both, working together, take to finish the work, which B alone can finish in 36 days?

15 days

A is 40% more efficient than B i.e;

\(\frac{A}{B}\) = \(\frac{140}{100}\) = \(\frac{7}{5}\)

⇒ Efficiency (A = 7, B = 5),

 B finishes work in 36 days

therefore, total work = 5 x 36 = 180      .. (Efficiency × Days = Total work)

⇒ Time taken to complete the work by working together = \(\frac{180}{7+5}\) = 

\(\frac{180}{12}\) = 15 days.