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suppose john is rolling a pair of standard dice until the dice roll sums to 8 three times. what is the probability that he will roll more than 4 times? for example, some sequences of rolls include: • (1, 2), (4, 6), (4, 4), (5, 3), (2, 5), (2, 3), (6, 2) • (4, 4), (2, 1), (4, 5), (6, 6), (5, 3), (4, 3), (5, 5), (4, 4)

User Masam
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Final answer:

To find the probability that John will roll more than 4 times until the sum of the dice rolls to 8 three times, we need to calculate the probability of rolling 8 three times or more in 4 or fewer rolls.

Step-by-step explanation:

To find the probability that John will roll more than 4 times until the sum of the dice rolls to 8 three times, we need to calculate the probability of rolling 8 three times or more in 4 or fewer rolls. Let's break it down:

First, calculate the probability of rolling a sum of 8 in one roll. There are 5 combinations that can result in a sum of 8: (2, 6), (3, 5), (4, 4), (5, 3), and (6, 2).

Next, calculate the probability of not rolling a sum of 8 in one roll. Since there are 36 possible outcomes when rolling two dice, and we already determined that there are 5 combinations that result in a sum of 8, there are 31 combinations that do not result in a sum of 8.

Now, we can calculate the probability of rolling a sum of 8 three times or more in 4 or fewer rolls. We can use the binomial probability formula, where n is the number of rolls (4), x is the number of successes (3), and p is the probability of success (calculated in step 1). Plugging in the values, we get:

P(X ≥ 3) = C(4, 3) * (31/36)^1 * (5/36)^3 + C(4, 4) * (31/36)^0 * (5/36)^4

Simplifying and calculating this, we find that the probability of rolling more than 4 times until the dice roll sums to 8 three times is approximately 0.0256, or 2.56%.

User Shades
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2 votes

Final answer:

The probability of rolling more than 4 times until the dice sum to 8 three times is 2.51%.

Step-by-step explanation:

To find the probability that john will roll more than 4 times, we need to calculate the probability of three 8-sum rolls and count the number of rolls it takes to achieve that. We can use the concept of geometric probability for this.

The probability of rolling a sum of 8 with a pair of dice is 5/36. This means that the probability of not rolling a sum of 8 is 1 - 5/36 = 31/36. To roll three 8-sums, the probability is (5/36) * (5/36) * (5/36) = 125/46656.

Now, we need to calculate the probability of rolling more than 4 times. The probability of rolling exactly 4 times is (31/36) * (31/36) * (31/36) * (5/36) = 14605/2985984. The probability of rolling more than 4 times is 1 - 14605/2985984 = 2.51%.

User Cacho Santa
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