In a lottery, there are 10 prizes and 25 blanks. A lottery is drawn at random. What is the probability of getting a prize?

Total number of outcomes possible, n(S) = 10 + 25 = 35

Total number of prizes, n(E) = 10

  $P\left(E\right)=\frac{n\left(E\right)}{n\left(S\right)}=\frac{10}{35}=\frac{2}{7}$