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Hi All,

In these types of 'rate' questions, it often helps to think in terms of the TOTAL work that must be done to complete the task. If a 10-man crew can complete the job in 110 days, then that means that (10)(110) = 1100 worker-days of effort are required to complete the job. That could be 1 worker working 1100 days, 2 workers working 550 days each, 2 workers working for 100 days and 90 other workers working for 10 days, etc.

We're told that there were 5 days of rain in the first 60 days, so the 10 workers worked for 55 days = (10)(55) = 550 worker-days of the 1100 required were completed. From that point on, there were 16 workers on the job each day; we can calculate how many days it would take those 16 workers to complete the task:

550/16 = 275/8 = 34 3/8 days needed to complete the job

We're told that the job was completed on day 100. Since that time period includes 100 - 60 = 40 days, and 35 (rounded up) days were needed to complete the work, then then 40 - 35 = 5 days were lost during that time due to rain.

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I think we can do it in a way to account lost work too.
Each person output 1 unit.

X => rainy days within 61st to 100.
So lost work is 5 days of rain before 61st, x days within in 61st to 100 and reduction of extra 10 days from 110 to 100.
Assumption was 10 people will work for whole 110 days. All above was expected of 10 workers.

Lost = 5*10+10*10+10*x

Compensation by extra 6 workers who work for 40-x days


150+10x=6(40-x)
150+10x=240-6x
90=16x
x=5.625

If x is higher we would need more workers or more days.
So x should be 5.
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