\(15*r*3\) = 1 unit of work. Thus, rate of each worker =\(\frac{1}{45}\)
The amount of work done in 1 day with all 15 workers =\(\frac{1}{3}\). The amount of work left to be done by (15-9) workers = \(\frac{2}{3}\)

Let them take d days to complete this work-->\(6*r*d\) = 2/3--> \(6*\frac{1}{45}*d =\frac{2}{3}\)--> d= 5 days.
A.
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Assume the order to be welding 45 rods...

Each welder works at 1 rod per day

On first day 15 rods are completed.

So now 30 rods have to be completed by 6 workers...

So, the answer is 30/6 = 5 days
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1. We need to find out the time taken by 6 workers after day 1.
2. total no.of wokers * total time taken = time taken by 1 worker
3. Time taken by 1 worker = 15*3 = 45 days
4. But on day 1 fifteen workers had already worked finishing 1/3 of the job. So 6 workers have to finish only 2/3 of the job.
5. Total time taken by 6 workers can be got from formula used at (2). i.e., 6* total time taken = 45. Total time taken by 6 workers to finish the complete job is 45/ 6 = 7.5 days.
6. Time taken by 6 workers to finish 2/3 of the job is 2/3 * 7.5 = 5 days.

The answer is choice A
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Holistic and Systematic Approach

sol:

15 welders rate of job = 1/3

W= 1 (1/3) = 1/3

Remaining Job = 1-(1/3) = 2/3

Job---days---number of welders

2/3------2----------15
2/3------X ---------15-9 = 6


X= 2* (15/6) =5 days

Let rate of each worker be \(\frac{1}{x}\)
For 15 workers the rate is \(\frac{15}{x}\)

\(\frac{15}{x}\) = \(\frac{1}{3}\)
Hence rate of each worker is \(\frac{1}{45}\)

After day 1, \(\frac{1}{3}\) of the work will be complete, hence \(\frac{2}{3}\) of the work remains
The number of workers has now dropped from 15 to 6 (Since 9 workers left)
Rate of 6 workers = \(\frac{6}{x}\) = 6 * \(\frac{1}{45}\) = \(\frac{2}{15}\)

W= \(\frac{2}{3}\) ; R = \(\frac{2}{15}\); T = \(\frac{W}{R}\)
T = 5

Answer is A
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Total work = 15*3 = 45 man days
1 st day = 15*1 = 15 man days

Rem work = 45-15 = 30 man days

This can be completetd in 30/6 = 5 days

15 Welders were supposed to do the job in 3 days but 9 of them left after one day. If none let left then whey will work 2 more days.

So 15 welders will do job in 2 days (because they already worked one day)
6 welders will need (15 x 2)/6= 5 Ans a.
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