Question

Two unbiased dice are rolled once. What is the probability of getting a sum equal to $7$

Answer 1

We know that when two unbiased dice are rolled once, the total number of possible outcomes is $6\times 6=36.\therefore n\left(S\right)=36$
Let $A$ be the event of getting a sum equal to $7$.
$A=\left\{\right(1,6),(2,5),(3,4),(4,3),(5,2),(6,1\left)\right\}\therefore n\left(B\right)=6$
$\therefore P\left(B\right)=\frac{n\left(B\right)}{n\left(S\right)}=\frac{6}{36}$