a pair of dice is rolled together till a sum of 6 or 8 is obtained.find the probability that 6 comes before 8.

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- Dec 6th 2009, 03:35 AMpsparmarprobability
a pair of dice is rolled together till a sum of 6 or 8 is obtained.find the probability that 6 comes before 8.

- Dec 6th 2009, 05:21 AMHallsofIvy
Since 6 and 8 are equally likely on any one roll, the probability that "6 comes before an 8" (which means that the sequence of rolls terminate on a roll of 6, not 8) is exactly the same as "8 comes before a 6". Since one of those two

**must**happen by the rules of this problem, their sum must be 1: each is equal to 1/2. - Dec 6th 2009, 11:17 AMSoroban
Hello, psparmar!

There is an "intuitive" solution for this.

Quote:

A pair of dice is rolled together till a sum of 6 or 8 is obtained.

Find the probability that 6 comes before 8.

Their probabilities are equal.

Either event is equally likely to happen.

Therefore, the probability that a sum of 6 precedes a sum of 8 is: .$\displaystyle \frac{1}{2}$