Question

A number is chosen at random from a first 25 natural number find the probability that the number is not prime​

Answer 1

Hi!

S = {1,2,3,...,25}

n(S) = 25

Let A be the event of not getting prime number less than 25

Let A' be the event of getting prime number less than 25

A' = {2,3,5,7,11,13,17,19,23}

n(A') = 9

P(A') = n(A')/n(S)

=9/25

P(A) = 1 - P(A')

= 1 - (9/25)

= (25-9)/25

= 16/25

Therefore, the probability that the number is not prime is 16/25

All the best :)