Question:
In a lottery there are 10 prizes and 25 blanks. What is the probability of getting a prize?
Solution:
Total number of lottery tickets = 10 + 25 = 35
Number of prizes = 10
Let E be the event of getting a prize.
$\therefore \mathrm{P}($ getting a prize $)=\mathrm{P}(\mathrm{E})=\frac{\text { Number of outcomes favourable to } \mathrm{E}}{\text { Number of all possible outcomes }}$
$=\frac{10}{35}=\frac{2}{7}$
Thus, the probability of getting a prize is $\frac{2}{7}$.