Question

Suppose that a person rolls two balanced dice three times in succession. determine the probability that on each of the three rolls, the sum of the two numbers that appear will be 7.

Answer 1

The number of combinations that will result in a sum of 7 is:

1 + 6

6 + 1

2 + 5

5 + 2

3 + 4

4 + 3

For a total of 6 combinations per roll. While the total number of combinations per roll are:

6 * 6 = 36

Hence the probability that the sum is 7 would be:

Probability = 6 / 36 = 1 / 6

For a succession of three times, the overall probability that each three rolls will be a sum of 7 is:

Overall probability = (1/6) * (1/6) * (1/6)

Overall probability = 1/216 = 4.63 x 10^-3 = 0.463%