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What is the standard deviation (d) of m, n, p?

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MathRevolution
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What is the standard deviation (d) of m, n, p? [#permalink] New post   09 Dec 2016, 01:52
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A
B
C
D
E

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25% (medium)

Question Stats:

66% (00:38) correct 34% (00:41) wrong based on 123 sessions
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What is the standard deviation (d) of m, n, p?

1) m, n, and p are different
2) \(d^2-2d=0\)
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C
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Omkar.kamat
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Re: What is the standard deviation (d) of m, n, p? [#permalink] New post   09 Dec 2016, 03:40
Statement 1 isn't enough as it just says three entities are different.

Statement 2 Can be enough if we derive d=2. Or another interpretation can be d=0 or d=2. If former is considered this is enough but in latter it's not.

Combining both of them, we know m,n,p are different hence d cannot be 0. Thus d=2.

Confused between (B) and (C)

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Re: What is the standard deviation (d) of m, n, p? [#permalink] New post   09 Dec 2016, 09:22
Hemanth2017 wrote:
Ans C..

Sent from my C6902 using GMAT Club Forum mobile app

Why not d=2 Directly from Statement 2 ?? Can you clear my confusion ??

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Re: What is the standard deviation (d) of m, n, p? [#permalink] New post   09 Dec 2016, 09:44
From Statement 2.. d=0 and d=2
So you have two answers for standard deviation..not sufficient to answer the question..

When you combine both statement u can confirm that d=2 because D cant be 0 as m,n,p are different..

So,option C

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Re: What is the standard deviation (d) of m, n, p? [#permalink] New post   12 Dec 2016, 01:13
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==> From the original condition, there are 3 variables, and therefore E is most likely to be the answer. By solving con 1) & con 2), from d(d-2)=0, you get d=0, 2. From con 1), m, n, and p are different and d≠0, it is always d=2 only, so it is unique and sufficient.

Therefore, the answer is C.

Answer: C
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Re: What is the standard deviation (d) of m, n, p? [#permalink] New post   22 Nov 2021, 12:16
MathRevolution wrote:
What is the standard deviation (d) of m, n, p?

1) m, n, and p are different
2) \(d^2-2d=0\)


Statement 1 Alone:

This only tells us the d > 0. Then statement 1 alone is insufficient.

Statement 2 Alone:

d = 2 or d = 0. A standard deviation could be 0 if we have repeating values only, so statement 2 is insufficient.

Both Statements Combined:

Since d > 0, we must have d = 2. Then combined it is sufficient.

Answer: C
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Re: What is the standard deviation (d) of m, n, p? [#permalink]
22 Nov 2021, 12:16
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