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# Basic probability

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Senior Manager
Joined: 23 Mar 2011
Posts: 462
Location: India
GPA: 2.5
WE: Operations (Hospitality and Tourism)

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24 Nov 2011, 11:22
Can somebody help me understand this basic of probability please? "What is the probability of throwing 2 fair dices, getting first number always greater than the second number" . Please note, its not a sum from any book, but was used in one of the classes I attended as an explanation, which I could not still follow.
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Director
Joined: 28 Jun 2011
Posts: 889

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24 Nov 2011, 11:51
"What is the probability of throwing 2 fair dices, getting first number always greater than the second number"

For example

probability for the 1st dice is 1/6

probability for the 2nd dice is 1 - 1/6 = 5/6

So first number always greater than the second number
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Joined: 05 Oct 2011
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24 Nov 2011, 13:18
1
KUDOS
Here are the all possible outcomes.

(1,1) (1,2) (1,3) (1,4) (1,5) (1,6)
(2,1) (2,2) (2,3) (2,4) (2,5) (2,6)
(3,1) (3,2) (3,3) (3,4) (3,5) (3,6)
(4,1) (4,2) (4,3) (4,4) (4,5) (4,6)
(5,1) (5,2) (5,3) (5,4) (5,5) (5,6)
(6,1) (6,2) (6,3) (6,4) (6,5) (6,6)

All possible outcomes = 36

Favorable outcomes are those in green above = 15

Probability = Favorable outcomes/All possible outcomes = 15/36 = 5/12
Senior Manager
Joined: 23 Mar 2011
Posts: 462
Location: India
GPA: 2.5
WE: Operations (Hospitality and Tourism)

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26 Nov 2011, 09:04
Hi Prateek, I made the same mistake. Icanwill is absolutely right, I started that way, guess did not consider all outcomes of the numbers like Icanwill did, so went wrong. 5/12 is correct. But there is another explanation to it.
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Re: Basic probability   [#permalink] 26 Nov 2011, 09:04
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