# If you roll 2 die, what is the probability that you will get a sum of 11? What about a sum of 5?

Nov 18, 2015

The probabilities are: $P \left(A\right) = \frac{1}{18}$; $P \left(B\right) = \frac{1}{9}$.

#### Explanation:

To calculate the probabilities we have to calculate the number of all elementary events first.

$\overline{\overline{\Omega}} = {6}^{2} = 36$

Event $A$-"sum of numbers is 11" consist of 2 elements:

A={(6,5);(5,6)},

so $P \left(A\right) = \frac{2}{36} = \frac{1}{18}$

Event $B$-"a sum of numbers is 5" consist of 4 elements:

B={(1,4);(2,3);(3,2);(4,1)}

so $P \left(B\right) = \frac{4}{36} = \frac{1}{9}$