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The Magic Cafe Forum Index » » Magical equations » » Help. Am I making this too simple? (0 Likes) Printer Friendly Version

El_Lamo
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Canada
589 Posts

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I have eight cards, six black and two red.
If the spectator randomly selects the cards, face down, one at a time... what are the odds that the last card will be red?

Is it 25%

Cheers - El Lamo
Life is a system of circumstance presented coincidently in an illusory way.
Hideo Kato
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Tokyo
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Although I don't know why you need this probability, the solution is simple. It is same as the probability in which a red card is selected as the first one. So you are right.

Hideo Kato
rgranville
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Boston area
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And since nobody asked, I'll give you the mathematical breakdown. Smile

In general, the number of different ways you can arrange 8 cards is 8!. Since 6 of your cards are black, we have to divide that number by 6! And since 2 of the cards are red, we have to divide again by 2! That leaves us with 28 different ways to arrange a packet of 6 black cards and 2 red cards.

Now how many of these arrangements have a red card as the last? Well, with the last card as red, that means we have to arrange the other 7. There are 7! ways to arrange 7 cards, and since 6 of them are black, we have to divide this by 6!. That leaves us with 7 ways to have the last card as red. Thus the odds are 7 out of 28, or 1 out of 4, or 25%.
:cucumber:
LobowolfXXX
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La Famiglia
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Quote:
On 2004-02-11 07:52, rgranville wrote:
And since nobody asked, I'll give you the mathematical breakdown. Smile


It's good practice. Way to go!
"Torture doesn't work" lol
Guess they forgot to tell Bill Buckley.

"...as we reason and love, we are able to hope. And hope enables us to resist those things that would enslave us."
Necromance
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Pattingham, UK
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Quote:
On 2004-02-11 07:52, rgranville wrote:
And since nobody asked, I'll give you the mathematical breakdown. Smile


Well done! I'm not a great fan of mathematics but that was certainly invigorating
Any sufficiently advanced technology is indistinguishable from magic-Arthur C. Clarke
Any technology distinguishable from magic is insufficiently advanced-probably NOT Arthur C. Clarke
Heinz Weber
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Austria
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There is always a way to do it more sophisticated!

Heinz
The Magic Cafe Forum Index » » Magical equations » » Help. Am I making this too simple? (0 Likes)
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