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  #1  
Old 06-28-2005, 03:01 PM
Macedon Macedon is offline
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Join Date: May 2004
Posts: 18
Default Probability Question

Just bought "Probability Demystified" by Allan Bluman and I came across this problem on page 71.

A die is rolled five times. What is the probability of getting 5 twos?
a. 1/8
b. 1/4
c. 1/6
d. 1/32

The answer, according to the key in the back of the book, is letter "d".

Now I thought the probability of getting 1 two on a die is 1/6. The probability of getting 2 twos after rolling the die twice should be 1/36, correct? So if you rolled the dice five times, shouldn't the probability of getting ALL twos be 1/7776?

What am I missing?
[Please don't embarass me with any "you idiot" comments. I'm trying to understand this stuff, and I happen to have a very non-mathematical like brain.]
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  #2  
Old 06-28-2005, 03:10 PM
Tom1975 Tom1975 is offline
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Join Date: Jun 2005
Posts: 132
Default Re: Probability Question

You're right. It sounds like the author was thinking of flipping a coin rather than rolling a die - the odds of getting 5 tails on 5 flips would be 1/32.
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  #3  
Old 06-29-2005, 01:26 AM
SumZero SumZero is offline
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Join Date: Jul 2004
Posts: 73
Default Re: Probability Question

You are missing the fact that the die in question has half its face labled with a two. [img]/images/graemlins/smile.gif[/img]

Yeah, that has to be an author error. If you enjoy dice questions check out this thread from STT.
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