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Riddle Me This

#226 harrythook Posted 28 October 2006 - 02:08 PM

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**note, yes, you do have to take into consideration that the men have paid \$9 each. **

Math class 101

I failed at math I guess
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#227 c7ng23 Posted 28 October 2006 - 10:46 PM

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Hi everyone,
I don't want to harp on the hat riddle but I believe I figured out a satisfactory answer. The first person simply says the color of hats that is even, since there is an odd number of people ahead of him (9) the combination of hat colors must consist of an even number of one color of hat and an odd number of another color of hat.

To illustrate here is an example. (When I say first person, second person, etc. I am starting from left to right)

W | W B B B W W B B B

The first person is only important in letting the others know what color hat they are wearing. In this situation the first person will say Black, since there is an even number of black hats. This means that there must be an odd number of white hats, as a mathematical principal (an odd number broken up in 2 whole numbers must consist of an even number and an odd number).

The second person will see that there are 6 B ahead, meaning that if he was black there would be an odd number of blacks. Therefore he is WHITE.

The third person knows there is 1 white behind him and since he sees 5 B ahead of him he knows he must be B to make the total number of B even.

This pattern continues so on and so fourth.

After considering this example you might ask what would happen in the following situation:

W| B B B B B B B B B

In this case, the first person would say white.

The second person would see that there 8 B ahead of him, meaning that if he were W it would still be an odd number of whites contradicting the first person, therefore he is B.

The third person would see 7 B ahead of him and knowing there was 1 B behind him and 7 B ahead, if he was white he would realize that there would still be an odd number of white contradicting the first person.

This occurs so on and so fourth so that everyone will know they are Black.

SO THE RULE IS:::::: Say the number of even hats, and if they are all odd (all the hats are the same color) say the opposite color
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Furthermore, with a slight alteration in rule, it is possible to save N-1 people for N number of total people (everyone can be saved except the first guy who gets the short straw unfortunately)

Let's take 2 cases.

Case 1 we already described for an even number of people, (it happened to be 10 in total).

Case 2 is for an odd number of people.

For an odd number of people there are the following possibilities:
2 groups both odd
2 groups both even
And to be thorough- 1 group even but that will fall into place as if 1 group was all odd as in above case.

This time, the first person will designate a color to stand for whether there are 2 groups of odd colors, or 2 groups of even colors.

Let's say that Black stands for Even and White stands for Odd

Again, the easiest way to illustrate is perhaps by example and for an example we shall choose a managable number to work with. There are 5 people.

B | W B B W

The first person will say Black since there are 2 groups of even (2 whites and 2 blacks)

The first person will see 1 W and will know he is W to make an even.

For 2 odds it can easily be seen the same will work (1st person will say black).

B | W W W W

The first person will say Black meaning there 2 groups of evens.

The second person will see that there are 3 W ahead of him. This is not possible to form 2 groups of evens. Therefore he assumes that they are all white as similar to Case I where n=even number.

Conclusion:
There are 2 possible cases. Case I: The total # of people is even. Case II: The total # of people is odd.

In Case I (2n from i=1 to i=infinity where i=1,2,3...etc.) the first person will say the color corresponding to the even number of hats. If there is only 1 group of odd hats, the person will say the opposite color.

In Case II (2n+1 from i=1 to i=infinity where i=1,2,3...etc.) the person will designate a color to signify two groups of even hats or a color to signify two groups of odd hats. If all hats are the same the person will say the color signifying two groups of evens.

Edited by c7ng23, 28 October 2006 - 10:48 PM.

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#228 silencedmessage Posted 29 October 2006 - 01:33 AM

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harrythook,
I think you might have missed that the bellboy kept \$2 extra, so that the men got even change.

also, i dont recall seeing any other riddles like this one in this topic, so im confused as to how it needs to be different?

skelly412,

You got it. Just to explain a little better, the issue is in the wording of the problem. as almost all riddles, it is misleading. When you say 9x3=27, you are actually subtracting 3 from the original 10; therefore, the goal is actually to get to 25, not 30. You would actually have to subtract the two to get a logical answer, which would be 25. nicely done. Your turn to post

-Silenced Message
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#229 skelly412 Posted 29 October 2006 - 10:50 AM

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sorry took so long:

I'm as small as an ant, as big as a whale. I'll approach like a breeeze, but can come like a gale. By some I get hit, but all have shown fear. I'll dance to the music, though I can't hear. Of names I have many, of names I have one. I'm as slow as a snail, but from me you can't run. What am I?
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#230 cheyenne 09 Posted 29 October 2006 - 07:30 PM

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#232 cheyenne 09 Posted 30 October 2006 - 04:20 AM

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Heres a quicky.....

On a fine sunny day a ship was in the harbor.
All of a sudden the ship began to sink.
There was no storm and nothing wrong with the ship,
yet it sank right in front of the spectators eyes.

What caused the ship to sink?
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#233 frantique Posted 30 October 2006 - 10:24 PM

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Was it a toy ship and somebody trod on it?
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#234 cheyenne 09 Posted 31 October 2006 - 01:16 AM

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Sorry.....Nope
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#235 ScHwErV Posted 31 October 2006 - 08:31 AM

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The ship is a submarine.
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#236 cheyenne 09 Posted 31 October 2006 - 01:12 PM

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Yeah.......The ship is a Submarine... " Captain ordered the crew to dive"

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#237 frantique Posted 31 October 2006 - 07:51 PM

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Crickey that is so obvious. And I thought about it for such a llooonnnggg time!
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#238 ScHwErV Posted 01 November 2006 - 02:50 PM

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In a conventional clock, how many times does the minute hand pass the hour hand between noon and midnight?
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#239 SNOWHITE Posted 01 November 2006 - 04:42 PM

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eleven ?
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#240 ScHwErV Posted 01 November 2006 - 08:39 PM

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