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Re: Is positive integer k the square of an integer? [#permalink]
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ccooley wrote:
I'm not entirely sure that it's outside the scope of the GMAT, because you can solve it with just reasoning and basic math.


You're absolutely right; it's not out of scope.

When I first created the question, statement 1 read "k = n!, where n is an integer greater than 1"
Then, as I was posting the question, I realized that making the number prime would require fewer words. In doing so, I made the question MUCH easier.
My bad.

Cheers,
Brent
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Is positive integer k the square of an integer? [#permalink]
GMATPrepNow wrote:
Is positive integer k the square of an integer?

1) k = p!, where p is a prime number
2) k + 1 = w² - 2w + 2, where w > 0

IMPORTANT: This question is beyond the scope of the GMAT. That said, most students will encounter GMAT math questions they can't answer (e.g., the above question). So, I'm curious about how you'd handle a question of this nature.

Share your thoughts!!


IF YOU FIND MY SOLUTION HELPFUL PLEASE GIVE ME KUDOS

(1) k = p! where p is a prime number. This means that p = 2,3,5,7.... let p =2 k =2, so we get a no. Let p=3, then k = 3*2 = 6 so we get another no. Let p =5, then k =5*4*3*2*1 = 1*120, let p = 7. Then k = 7*6*5*4*3*2*1. The pattern that the test is trying to get you to see here, is that no matter what prime we pick, we will have a single leading prime factor, thus K can never be the square of an integer sufficient

(2) k+1 = w^2-2w+2 = (w-1)^2. Notice that there are no restrictions on w, or (w-1)^2 directly. Our only restriction is that k must be a positive integer.Then let (w-1)^2 = 0, (obtained when w=1)

This is an upper level 700 question for sure, but not nearly as bad as some of the 3 overlapping set problems. In my opinion, it is not unrealistic for an upper level test taker to run into a problem like this on test day.
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Is positive integer k the square of an integer? [#permalink]
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