Math Is Fun Forum

JaneFairfax

Member

Registered: 2007-02-23

Posts: 6,868

Problem from AoPS

bobbym

bumpkin

From: Bumpkinland

Registered: 2009-04-12

Posts: 109,606

Re: Problem from AoPS

Hi Jane;

Last edited by bobbym (2009-07-25 04:03:57)

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In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

JaneFairfax

Member

Registered: 2007-02-23

Posts: 6,868

Re: Problem from AoPS

This problem was posted here:

http://www.artofproblemsolving.com/Foru … p?t=290918

herefishyfishy1 doesn’t think itiselizabeth’s solution is correct but itiselizabeth’s solution looks fine to me. What do you think?

bobbym

bumpkin

From: Bumpkinland

Registered: 2009-04-12

Posts: 109,606

Re: Problem from AoPS

Hi Jane;

Her answer of 217 is correct and her method looks to me to be the principle of inclusion and exclusion. Her work is close to the book I mentioned. Fejda at the bottom of that page is also using the book idea but he doesn't seem to understand it.

Last edited by bobbym (2009-07-25 05:03:08)

---

In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

JaneFairfax

Member

Registered: 2007-02-23

Posts: 6,868

Re: Problem from AoPS

Thanks!

I must say I haven’t a clue what fedja is doing there.

bobbym

bumpkin

From: Bumpkinland

Registered: 2009-04-12

Posts: 109,606

Re: Problem from AoPS

Hi Jane;

I don't know why anyone ever buys a book anymore. Here is an excerpt from the book !!!!
It covers all of this.

http://books.google.com/books?id=jnyslkIXe5YC&pg=PA20&lpg=PA2&ots=R6i9C67U6w&dq=istvan+reiman+and+math

Last edited by bobbym (2009-07-25 05:11:34)

---

In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

JaneFairfax

Member

Registered: 2007-02-23

Posts: 6,868

Re: Problem from AoPS

Thanks for the Google link. itiselizabeth has just posted again, explaining her solution in more detail. Her method appears to be different from the one in the book – at any rate, her counting method for the first part looks to be much better.

bobbym

bumpkin

From: Bumpkinland

Registered: 2009-04-12

Posts: 109,606

Re: Problem from AoPS

Hi Jane;

Her method does seem better than the book. What do you think of the poster itiselizabeth, is she reliable? She seems to have good problem solving skills. Her style seems familiar to me but I just can't place it.

Last edited by bobbym (2009-07-25 09:54:29)

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In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.