Find the probability of rolling a sum of 6 or 11 when rolling two number cubes. Enter your response as a fraction.

1 answer

To find the probability of rolling a sum of 6 or 11 with two number cubes (dice), we first need to determine the total number of possible outcomes when rolling the dice.

Each die has 6 faces, so the total number of possible outcomes when rolling two dice is:

\[ 6 \times 6 = 36 \]

Next, we will find the number of ways to achieve a sum of 6 and a sum of 11.

Sum of 6

The combinations of dice that yield a sum of 6 are:

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

Counting these combinations, we have 5 outcomes that result in a sum of 6.

Sum of 11

The combinations of dice that yield a sum of 11 are:

  • (5, 6)
  • (6, 5)

Counting these combinations, we have 2 outcomes that result in a sum of 11.

Total Successful Outcomes

Now we add the successful outcomes for both sums:

  • Sum of 6: 5 outcomes
  • Sum of 11: 2 outcomes

Total successful outcomes = \( 5 + 2 = 7 \)

Probability

Now we can calculate the probability of rolling a sum of 6 or 11:

\[ \text{Probability} = \frac{\text{Number of successful outcomes}}{\text{Total number of outcomes}} = \frac{7}{36} \]

Thus, the probability of rolling a sum of 6 or 11 when rolling two number cubes is:

\[ \boxed{\frac{7}{36}} \]