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GMAT PREP DS question

Problem Solving — algebra and arithmetic (GMAT Focus Edition)
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GMAT PREP DS question

by alex.gellatly » Mon Apr 16, 2012 12:52 am
If p and n are positive integers and p > n, what is the remainder when p2 - n2 is divided by 15 ?

(1) The remainder when p + n is divided by 5 is 1.

(2) The remainder when p - n is divided by 3 is 1.

Thanks in advanced
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by killer1387 » Mon Apr 16, 2012 1:01 am
alex.gellatly wrote:If p and n are positive integers and p > n, what is the remainder when p2 - n2 is divided by 15 ?

(1) The remainder when p + n is divided by 5 is 1.

(2) The remainder when p - n is divided by 3 is 1.

Thanks in advanced
(p+n)*(p-n)
1) no info for 3 and p-n
Insufficient

2) no info for 5 and p+n
insufficient

1) and 2)
we cant say anything about overall 15 for two (p-n) and (p+n)

Hence E
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by seal4913 » Mon Apr 16, 2012 5:25 pm
alex.gellatly wrote:If p and n are positive integers and p > n, what is the remainder when p2 - n2 is divided by 15 ?
The question is what is the remainder when p^2 - n^2 is divided by 15. It's nice to see killer get it right even with the wrongly worded question ;)
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by killer1387 » Tue Apr 17, 2012 12:50 am
seal4913 wrote:
alex.gellatly wrote:If p and n are positive integers and p > n, what is the remainder when p2 - n2 is divided by 15 ?
The question is what is the remainder when p^2 - n^2 is divided by 15. It's nice to see killer get it right even with the wrongly worded question ;)
cant find anything wrongly worded. question is correct.
If you are talking of p^2 and p2 then yeah i have seen posts here using the same representation so took it p^2 :)
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