Question

Zubin and Pravin can individually complete a job in 36 min and 60 min respectively. Starting with Zubin, they work alternately for a minute each till the work is completed, only the one working at the end allowed to work for less than a minute in his final turn. How long will it take the due to complete the job?
1. 45 min
2. 44min 48 s
3. 44 min 45 s
4. 45 min 12 s

Answer 1

Correct Answer - Option 2 : 44min 48 s

Given:

Zubin and Pravin can individually complete the job in 36 min and 60 min respectively. Starting with Zubin, they work alternately for a minute.

Concept Used:

If A and B can do a task alone in x min and y min respectively then total work = LCM of x and y

Calculation:

Total work = LCM of 36 and 60 = 180 units

Efficiency of Zubin = 180/36 = 5

Efficiency of Pravin = 180/60 = 3

Starting with Zubin they can do (5 + 3) = 8 unit of the task in (1 + 1) = 2 min

Now, 8 × 22 = 176

⇒ In an alternative minute, they together can do 176 unit task in (2 × 22) = 44 minutes

Remaining work = (180 - 176) = 4 unit

At the end of 44 minutes, Zubin will start to do the work

Zubin can do 5 unit task in 1 minute i.e in 60 second

⇒ To complete the remaining 4 unit task Zubin will take (4/5) × 60 = 48 second

Total time to complete the task (44 min + 48 second) = 44 Minutes 48 Seconds

∴ They will take 44 min 48 seconds to complete the task.