GIVEN: A and B together can finish a work in 15 days and ratio of efficiency of A to B is 5 : 3. CALCULATION: Ratio of efficiency of A to B = 5 : 3 Ratio of time taken by A to B = 3 : 5 Let time taken by A and B alone to finish the work is ‘3x’ and ‘5x’ respectively. Now,
1
3x
+
1
5x
=
1
15
⇒
5+3
15x
=
1
15
⇒ x = 8 ∴ Time taken by A alone to finish the work =3x=24 days