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seen Jun 5 '12 at 14:52

Apr
20
revised Prove that two sides are parallel in the reflection of an isosceles triangle
Grammar
Apr
20
asked Prove that two sides are parallel in the reflection of an isosceles triangle
Feb
8
comment Pigeonhole principle and sequences problem
Great! This is actually a problem I had to do in my discrete math exam last week. As I couldn't wait until we get the final grading I decided to post my approach here.
Feb
8
accepted Pigeonhole principle and sequences problem
Feb
8
revised Pigeonhole principle and sequences problem
Clarify approach
Feb
8
asked Pigeonhole principle and sequences problem
Feb
1
awarded  Editor
Feb
1
revised Prove that $n=2^k -1$ is not a prime number, with $k=ab$. (Edit: $a\not=1$ and $b\not=1$)
edited title
Jan
31
awarded  Scholar
Jan
31
comment Prove that $n=2^k -1$ is not a prime number, with $k=ab$. (Edit: $a\not=1$ and $b\not=1$)
Got it. Thank you very much.
Jan
31
accepted Prove that $n=2^k -1$ is not a prime number, with $k=ab$. (Edit: $a\not=1$ and $b\not=1$)
Jan
31
comment Prove that $n=2^k -1$ is not a prime number, with $k=ab$. (Edit: $a\not=1$ and $b\not=1$)
I'm sorry I didn't state that $ab$ is a non-trivial factorisation.
Jan
31
asked Prove that $n=2^k -1$ is not a prime number, with $k=ab$. (Edit: $a\not=1$ and $b\not=1$)
Dec
28
comment Pigeonhole principle problem
That's very simple! I was trying to fit in the pigeonhole principle as I could, but this is even more obvious.
Dec
28
comment Pigeonhole principle problem
Thank you so much! I only used the integer clue to assume that every day he trained a positive integer number of hours.
Dec
28
comment Pigeonhole principle problem
Ops. Sorry I saw the reference to using Latex after I posted the last comment. I'll do that next time. Thanks for the heads up.
Dec
28
comment Pigeonhole principle problem
OK. I think I got it now. We know that at least one pair is > 18. And as the problem states that he trained an integer number of hours, it has to be, at least, 19 hours. The grouping issue that Kannappan points out, can be solved if we group it like this: {1,12}, {2,3}, {4,5},{6,7},{8,9},{10,11}. This way we cover all the possible pairs and we can apply the same principle.
Dec
28
comment Pigeonhole principle problem
Wouldn't we need to leave {12,1} out?
Dec
28
awarded  Student
Dec
28
asked Pigeonhole principle problem