Q) If p is a positive is p > 4 ?
1) p^4 = 256
2) (p^2 - 1)(p - 4) >0
I get Statement 1 is sufficient.But how's statement 2 sufficient ? Answer is D
Thanks
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Inequality DS ; Little help
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soni_pallavi
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jkaustubh
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Statement 2 is not sufficient
as the inequality can be satisfied by the following ranges
p-> (-1,1)U(4,infinity)
for eg.
P=0 satisfies the inequality and also any value of p greater than 4
hence this statement is insufficient.
The OA should be A and not D
what is the source of the problem??
as the inequality can be satisfied by the following ranges
p-> (-1,1)U(4,infinity)
for eg.
P=0 satisfies the inequality and also any value of p greater than 4
hence this statement is insufficient.
The OA should be A and not D
what is the source of the problem??
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soni_pallavi
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Its from a mock test given to us at an institute...
I chose A ; the answer at the back is D.
Need an expert's advice to clarify this.
I chose A ; the answer at the back is D.
Need an expert's advice to clarify this.
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Brent@GMATPrepNow
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Target question: Is p > 4 ?soni_pallavi wrote:Q) If p is a positive is p > 4 ?
1) p^4 = 256
2) (p^2 - 1)(p - 4) > 0
Statement 1: p^4 = 256
256 = (4)(4)(4)(4)
So, if p^4 = 256 (and p is positive), then we can be certain that p = 4
Once we know the value of p, we can answer the target question with certainty, which means statement 1 is SUFFICIENT
Statement 2: (p^2 - 1)(p - 4) > 0
Factor to get: (p-1)(p+1)(p-4) > 0
There are several values of p that meet this condition. Here are two:
Case a: p = 1/2 in which case p is not greater than 4
Case b: p = 5 in which case p is greater than 4
Since we cannot answer the target question with certainty, statement 2 is NOT SUFFICIENT
Aside: jkaustubh noted that p=0 satisfies the given inequality, but the question tells us that p is positive. As such, p cannot equal 0
Answer = A
Cheers,
Brent
Brent Hanneson - Creator of GMATPrepNow.com
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jkaustubh
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Thanks Brent for reminding me that 0 is not positive. I always make this mistake.
Thank you
Thank you
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soni_pallavi
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Hi Brent
I just noticed I forgot to mention that in the question,P is a positive integer...Hence the answer should infact be D
I just noticed I forgot to mention that in the question,P is a positive integer...Hence the answer should infact be D
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Brent@GMATPrepNow
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Agreed. If the question had read...soni_pallavi wrote:Hi Brent
I just noticed I forgot to mention that in the question,P is a positive integer...Hence the answer should infact be D
If p is a positive integer, is p > 4 ?
1) p^4 = 256
2) (p^2 - 1)(p - 4) > 0
...the answer would have been D
Cheers,
Brent
Brent Hanneson - Creator of GMATPrepNow.com
