Re: Probability question
- From: "Proginoskes" <CCHeckman@xxxxxxxxx>
- Date: 2 Oct 2006 15:00:27 -0700
Luke Wu wrote:
A pair of dice, one red and one white, are rolled two successive times.
a) What is the probability that the sum of the two dice is the same on
both rolls?
b) What is the probability that the sum of the two dice is greater on
second roll?
I think I have part a) undestood.
Sample space would have 36 x 36 possible points that represent sums
(some sums appear more than once to make points all equally likely).
Because first pair can have 36 different (equally likely) sums and so
can second pair.
The even we desire has 36 x 1 = 36 points (because second pair must
have same sum).
Therefore prob = 1/36
No, this is the probability of the same outcome on both rolls.
To find the probability that the sums are the same, you can break the
desired outcomes into eleven cases:
* Sum = 2 both times (P = 1 / 36^2)
* Sum = 3 both times (P = 2*2 / 36^2)
* Sum = 4 both times (P = 3*3 / 36^2)
etc
The final answer is (2*(1 + 4 + 9 + 16 + 25) + 36) / 36^2 = 73 / 648.
Someone pointed out that if the answer to (a) is p, then the answer to
(b) is 0.5*(1-p), so the answer to (b) is 575 / 36^2.
--- Christopher Heckman
.
- References:
- Probability question
- From: Luke Wu
- Probability question
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