Question

Which of the following shows the correct calculation for finding the probability of rolling two number cubes and getting a sum of 6 or 11? (1 point)

5/36 • 2/36
5/36 + 2/36
6/36 • 2/36
6/36 + 2/36

Answer 1

To find the probability of rolling two number cubes (or dice) and getting a sum of 6 or 11, we need to add the probabilities of each individual event.

1. First, we need to determine the probabilities of getting a sum of 6 and a sum of 11 when rolling two dice.

- The combinations that result in a sum of 6 are:
- (1, 5)
- (2, 4)
- (3, 3)
- (4, 2)
- (5, 1)

This gives us 5 combinations.

- The combinations that result in a sum of 11 are:
- (5, 6)
- (6, 5)

This gives us 2 combinations.

2. The total number of outcomes when rolling two dice is 6 * 6 = 36.

3. Now we calculate the probabilities:
- The probability of rolling a sum of 6 is 5/36.
- The probability of rolling a sum of 11 is 2/36.

4. To find the probability of rolling a sum of either 6 or 11, we add these probabilities together:
\[
P(6 \text{ or } 11) = P(6) + P(11) = \frac{5}{36} + \frac{2}{36} = \frac{7}{36}
\]

Now we can identify the correct expression from the given options:

- 5/36 • 2/36 (incorrect)
- 5/36 + 2/36 (correct)
- 6/36 • 2/36 (incorrect)
- 6/36 + 2/36 (incorrect)

The correct calculation is **5/36 + 2/36**.