A researcher has determined that she requires a minimum of n

[rsarashi]

A researcher has determined that she requires a minimum of n responses to a survey for the results to be valid. If p% of the surveyed individuals fail to respond to the survey, how many individuals, in terms of n and p, must the researcher survey to produce twice the minimum required number of responses?

A) 200n/100-p

B) 2n/100-p

C) 200n/p

D) 2n(100+p)/100

E) 2n+2np/100

OAA

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Hi rsarashi,

This question was discussed here:

https://www.beatthegmat.com/a-researcher ... 85176.html

GMAT assassins aren't born, they're made,
Rich

[Matt@VeritasPrep]

If we send out x surveys, we know that (1 - p/100), or (100 - p)/100 people will respond.

We want that number to be at least 2n, so

x * (100 - p)/100 = 2n

x = 2n * 100 / (100 - p)

and our answer is A.

[Matt@VeritasPrep]

We could also always pick our own numbers: this is a great, mostly foolproof way to get the answer on the test when you either can't set up the algebra or fear that you've written the wrong equation.

Suppose n = 50 and p = 20. Then we're going to need 125 surveys.

Plugging n = 50 and p = 20 into the answers, we want the answer that gives 125. A works, so we're set!

[Scott@TargetTestPrep]

A researcher has determined that she requires a minimum of n responses to a survey for the results to be valid. If p% of the surveyed individuals fail to respond to the survey, how many individuals, in terms of n and p, must the researcher survey to produce twice the minimum required number of responses?

A) 200n/100-p

B) 2n/100-p

C) 200n/p

D) 2n(100+p)/100

E) 2n+2np/100

OAA

Let x = total number of people she surveys. Therefore, we have:

x(1 - p/100) = 2n

x(100 - p)/100 = 2n

x = 2n * 100/(100 - p)

x = 200n/(100 - p)

Answer: A