Given: A and B together can complete a particular task in 4 days. And A alone can complete the same task in 6 days. Calculation: According to the question: Work done by (A + B) in 4 days ⇒ Work done by (A + B) in 1 days = 1/4 Again, Work done by A alone in 6 days. ⇒ Work done by A alone in 1 days =1/6 Work done by B alone in 1 days =(1/4)–(1/6) ⇒(3–2)/12 ⇒1/12 ∴ The total time taken by B to complete the work is 12 days. A + B = 4 days A = 6 days L..C.M (4 , 6) = 12 ⇒ A + B = 4 days (A + B) efficiency =12/4=3 ⇒ A = 6 days A efficiency =12/6=2 So B efficiency =3−2=1 ⇒B=12/1=12 days ∴ The total time taken by B to complete the work is 12 days.