Correct Answer - Option 2 : 36 days
CALCULATION:
If Ashit takes 'a' days to complete the whole work, then Biswas will take (a + 12) days to complete the whole work.
As Biswas has completed 60% of the work, the remaining 40% work is completed by Ashit.
∵ Ashit has done 40% of the work before leaving.
∴ Ashit has worked for 2a/5 days.
∵ Biswas has completed 60% of the total work
∴ Biswas has worked for [3(a + 12)]/5 days.
But as Ashit leaves the work 12 days before the Biswas.
⇒ No. of days for which Biswas works = No. of days for which Ashit works + 12
⇒ [3(a + 12)]/5 = (2a/5) + 12
⇒ 3a + 36 = 2a + 60
⇒ a = 24 days
∴ Time taken by Biswas to complete the work independently = (a + 12) = (24 + 12) = 36 days
- The key to solving this problem is to start from work completed by Biswas.
- The time taken to complete the work ∝ Amount of work.
- Efficiency ∝ 1/Time Taken to complete the work.