Bunuel wrote:
If a certain computer program scans a total of 5,760 files when it runs, how many minutes will it take to complete the scan?
(1) The program scans 8 files per second.
(2) It takes 3 times as long to run the scan as it takes to upload the output to a server, and it takes a total of 16 minutes to do both.
Forget conventional ways of solving math questions. For DS problems, the VA (Variable Approach) method is the quickest and easiest way to find the answer without actually solving the problem. Remember that equal numbers of variables and independent equations ensure a solution.
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The first step of the VA (Variable Approach) method is to modify the original condition and the question. We then recheck the question. We should simplify conditions if necessary.
This question is a work rate question. Remind that we have \(R = \frac{W}{T}\) where \(R\) is a work rate, \(W\) is an amount of work and \(T\) is a time it takes.
We can put \(W = 5760\) since we have a total of 5,760 files.
Since we have 3 variables (\(R\), \(W\) and \(T\)) and 2 equations, \(R=\frac{W}{T}\) and \(W=5760\), D is most likely to be the answer. So, we should consider each condition on its own first.
Condition 1)
\(R = 8\) files / second \(= 480\) files / minutes.
\(T = \frac{W}{R} = \frac{5760}{480} = 12\) minutes.
Since condition 1) yields a unique answer, it is sufficient.
Condition 2)
Since \(T\) is the scan time and the upload time is \(\frac{T}{3}\), we have \((\frac{4}{3})T = 16\) or \(T=12\).
Since condition 2) yields a unique answer, it is sufficient.
Therefore, D is the answer.
If the original condition includes “1 variable”, or “2 variables and 1 equation”, or “3 variables and 2 equations” etc., one more equation is required to answer the question. If each of conditions 1) and 2) provide an additional equation, there is a 59% chance that D is the answer, a 38% chance that A or B is the answer, and a 3% chance that the answer is C or E. Thus, answer D (conditions 1) and 2), when applied separately, are sufficient to answer the question) is most likely, but there may be cases where the answer is A,B,C or E.