1. one machine can finish in 60hrs. So one machines hour rate 1/60. for 12 machines it will be 12/60 = 1/5 per hour.
So it can finish in 5 hrs,
Sufficient

2.10 machines can complete in 6 hrs
so total 60 hours will take to complete the order for a machine.
the same method as above can be followed to determine the hours.
Sufficient

Ans D
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D


Machines are running at identical rate

(a) Sufficient. 1 Machine take 60 hours to fill order.... so rate = 1/60... so it would take 5 hours to complete the order by 12 machines
(b) Sufficient ... 10 machines take 6 hrs... so rate =1/60... so it would take 5 hrs to complete

Answer is D

1 machine takes 60 hrs so 12 machines take 60/12=5 hrs A suff.
10 machines take 6 hrs so 12 machines will take 10*6/12 =5 hrs. B suff
Hence D

I would like to point out that every post on this thread so far has figured out the exact time it will take the 12 machines to complete this order. Data sufficiency is not about finding the exact time it takes. Data sufficiency is about knowing that you will get one definite answer. For many questions, finding out the exact number is a waste of time.

For this problem, you have 3 variables: Output, rate, and time. (Output = rate * time)
You know that you need 2 of the 3 variables in order to get one definite answer.

The question stem gives you almost enough for rate, but not quite enough. It does let you know that all of the rates are the same. So if you get the rate for one machine, you have the rate for all the machines.

The first stimulus gives you the rate and the time for one machine. This will be the same for all the machines. Since it gives you 2 of the 3 variables, the first stimulus is sufficient.

The second stimulus gives you the rate and time for ten machines. You know that you can get the information for the individual machines because the rates are the same for all. Since it gives you 2 of the 3 variables, the second stimulus is sufficient.

The answer is D.

Notice that you don't have to calculate anything for this problem to get the answer. You just have to recognize what information you need, and know when that information is provided. Calculating the exact time it takes for the 12 machines is a waste of time for this problem.

Again, I just want to point out that data sufficiency is, much of the time, not about calculating the exact answer. Data sufficiency is about knowing that you have enough information to get one definite answer.

Hope this helps!

hi Bunuel

One doubt...

If the question stem states different rates for machines then B is not sufficient right??????

From (1)


So, let total work be 60 units
Thus 12 machines will take \(\frac{60}{12} = 5\ hours\)

From (2)


So, let total work be 60 units
Thus 12 machines will take \(\frac{60}{12} = 5\ hours\)

Thus EACH statement ALONE is sufficient to answer the question asked, answer will be (D)
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