Correct Answer - Option 4 : 5/12
Given-
Time taken by A to do a work = 12 days
Time taken by B to do the same work = 16 days
Concept Used-
Total Work = Efficiency × Total Time
Calculation-
Let the total work be 48 units.
Efficiency of A = 48/12
⇒ 4
Efficiency of B = 48/16
⇒ 3
Work done them in 4 days = 4 × (4 + 3)
⇒ 28 units
Left Work = 48 - 28
⇒ 20 units
∴ Fraction of work that is left = 20/48
⇒ 5/12