A completes 20% of a work in 5 days and B completes one-third of the work in 5 days. They began the work together but B leaves after 3 days. The total number of days needed for completion of the work is:

20

A = 20% of W = 5 days = 25 days,

B = \(\frac{1}{3}\)W = 5 days = 15 days,

⇒ A + B worked for 3 days and the B left = (3 + 5) x 3 = 8 x 3 = 24 units,   ..(Efficiency × Days = Total work)

⇒ Remaining Units = 75 - 24 = 51 units,

⇒ Time taken by A to complete the remaining work = \(\frac{51}{3}\) = 17 days,     ..(\(\frac{Work}{Efficiency}\) = Time)

⇒ Total time taken to complete the total work = 3 + 17 = 20 days,