Example 2. All natural numbers from 1 to 30 are written on identical cards and placed in an urn. After thoroughly mixing the cards, one card is drawn from the urn. What is the probability that the number on the drawn card will be a multiple of $5?$
Solution. Let $A$ be the event "the number on the taken card is divisible by 5". In this trial, there are 30 equally likely elementary outcomes, of which 6 outcomes are favorable to event $A$ (the numbers $5,10,15,20,25,30$). Therefore,

$$
P(A)=\frac{6}{30}=0.2
$$