If it is assumed that each of the n/4 production workers in a factory

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I did it in guesswork way sing the options had drastically different structures.

TO calculate work done we would have to multiple Rate * time.

And as per the question the rate will always be (something)/ t

This eliminated choices B C D. We are left with A and E.

E has 8.5n/60t. Since we have been given that "t" is Minutes. It would be a nonsensical value derived from 8.5 hours / 60 minutes * t minutes

So eliminated E. And got left with A.

This was my strategy to get the right answer. Although I did spent some making sure with a Rate-Time-Work table setup.

This question is poorly written, in my opinion.

I would interpret 50% faster as meaning producing 1 unit in 50% of the time.

The answer depends on the interpretation as producing 50% more product in the same time.

The question should be written as "50% more productive"

Posted from my mobile device

We have to assume that the total number of workers in the factory is n, because, otherwise, the problem would be unsolvable.

In the slow subgroup (which consists of n/4 workers), we have:

rate of 1 worker = work/time = 1/t items per minute
rate of n/4 workers = (n/4)(1/t) = n/4t items per minute

time = 8.5 hours = 510 minutes
total work = rate × time = (n/4t)(510) = 510n/4t items

In the fast subgroup (which consists of 3n/4 workers), we have:

rate of 1 worker = (3/2)(1/t) = 3/2t items per minute
rate of 3n/4 workers = (3n/4)(3/2t) = 9n/8t items per minute

time = 8.5 hours = 510 minutes
total work = rate × time = (9n/8t)(510) = 2295n/4t items

So, the total work done by the two subgroups in 8.5 hours is:

510n/4t + 2295n/4t = 2805n/4t items

Answer: A