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11 replies to this topic

### #1 sandstorm

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Posted 20 March 2008 - 03:02 AM

I got this one out of a book by the name of Math Magic (I think). It did not provide an answer, so I don't even know what it is. Give it a try!

“An odd number plus an odd number is an even number, and an even number
plus an odd number is an odd number. OK?”
“OK.”
“An even number plus an even number is an even number. OK?”
“Of course.”
“An odd number times an odd number is an odd number, and an odd number
times an even number is an even number. OK?”
“Yes.”
“Then an even number times an even number is an odd number. OK?”
“No! It is an even number.”
“No! It is an odd number! I can prove it!”

How?
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### #2 brhan

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Posted 20 March 2008 - 12:23 PM

Spoiler for not sure ...

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### #3 sandstorm

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Posted 20 March 2008 - 05:05 PM

...perhaps...

Edited by sandstorm, 20 March 2008 - 05:05 PM.

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### #4 statman

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Posted 20 March 2008 - 05:41 PM

I got this one out of a book by the name of Math Magic (I think). It did not provide an answer, so I don't even know what it is. Give it a try!

“An odd number plus an odd number is an even number, and an even number
plus an odd number is an odd number. OK?”
“OK.”
“An even number plus an even number is an even number. OK?”
“Of course.”
“An odd number times an odd number is an odd number, and an odd number
times an even number is an even number. OK?”
“Yes.”
“Then an even number times an even number is an odd number. OK?”
“No! It is an even number.”
“No! It is an odd number! I can prove it!”

How?

Spoiler for guess

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### #5 brhan

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Posted 20 March 2008 - 05:58 PM

5. O*E=E OK
Q: E*E=O?

so how about
E*E=(O or E): (E/O)*(E/O)=(O or E): E*E=O*(O or E) E*E=O*O or O*E, so E*E=O or O so E*E=O

From (5) O*E is E not O ...
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### #6 statman

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Posted 20 March 2008 - 06:15 PM

From (5) O*E is E not O ...

Thank you, I was trying to do this too quickly.
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### #7 Noct

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Posted 20 March 2008 - 06:58 PM

Spoiler for not sure ...

You didn't expand the binomial correctly

(odd+odd)*(odd*even) = (odd*odd) + (odd*odd) + (odd*even) + (odd*even)

That is not true.
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### #8 sandstorm

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Posted 21 March 2008 - 02:04 AM

Wow, I'm glad I posted this here. I would have never gotten the answer otherwise!
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### #9 brhan

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Posted 21 March 2008 - 12:10 PM

You didn't expand the binomial correctly

(odd+odd)*(odd*even) = (odd*odd) + (odd*odd) + (odd*even) + (odd*even)

That is not true.

Thanks, I agree it is not true. This one should work.
Spoiler for 2nd attempt

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### #10 bonanova

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Posted 21 March 2008 - 12:37 PM

v. O*E = E ==> E/E=O

The inference is not always true:
18/6 = 3
24/6 = 4
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The greatest challenge to any thinker is stating the problem in a way that will allow a solution.
- Bertrand Russell

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