Find the probability that a number selected from the number
Question:

Find the probability that a number selected from the number 1 to 25 is not a prime number when each of the given numbers is equally likely to be selected.

Solution:

GIVEN: A number is selected from numbers 1 to 25

TO FIND: Probability of getting a number which is not a prime.

Total number of cards is 25.

Total number of elementary events = 25

Cards bearing non prime numbers are 1,4,6,8,9,10,12,14,15,16,18,20,21,22,24, 25

Total number of cards bearing non-prime numbers = 16

Number of favourable elementary events = 16

We know that, Probability $=\frac{\text { number of favourable elementary events }}{\text { Total number of elementary events }}$

So, $P$ (getting a card bearing a non prime number) $=\frac{16}{25}$