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Each week we'll be posting several questions from The Official Guide for GMAT® Review, 13th Edition and then after couple of days we'll provide Official Answer (OA) to them along with a slution.
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Since t = 11 seconds represents time, one can immediately eliminate answers C,D and E, because they don't have units of time. (C) x/(ty) has units of 1/time (D) t/(xy) has units of time/speed squared, which finally is time cubed/distance squared (E) xy/t has units of speed squared/time, which finally is distance squared/time cubed
To choose between (A) and (B), we should keep in mind that time is distance/speed. Since the distance in our case is x, it should appear in the numerator.
Hence, Answer A.
PhD in Applied Mathematics Love GMAT Quant questions and running.
This problem is testing us on the Rate x Time = Distance relationship. This relationship also tells us that Rate = Distance/Time and Time = Distance/Rate.
Ultimately, we are looking for how many seconds it will take Juan to run x yards. Thus, the equation we’ll use is: Time = Distance/Rate. We know the distance is x yards, and we need to find Juan’s rate.
We can find Juan’s rate as follows: Rate = Distance/Time = y yards/11 seconds
Using that rate, we need to determine how long it takes him to run x yards at the same rate. So we have:
Time = Distance/Rate
Time = x yards/(y yards/11 seconds)
Time = (x yards) x (11 seconds/y yards)
Time = 11x/y seconds
Jeffrey Miller Jeffrey Miller Head of GMAT Instruction
Re: If Juan takes 11 seconds to run y yards, how many seconds
27 May 2016, 06:18