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.

Answer 1

Total no. of possible outcomes = 25 {1, 2, 3, … 25}

E ⟶ event of getting a prime no.

No. of favourable outcomes = 9 {2, 3, 5, 7, 11, 13, 17, 19, 23}

Probability, P(E) =`"No.of favorable outcomes"/"Total no.of possible outcomes"` =9/25

(`barE`) ⟶ 𝑒𝑣𝑒𝑛𝑡 𝑜𝑓 𝑛𝑜𝑡 𝑔𝑒𝑡𝑡𝑖𝑛𝑔 𝑎 𝑝𝑟𝑖𝑚𝑒 𝑛𝑜.

𝑃(`barE` ) = 1 − 𝑃(𝐸)

= 1 − 9/25 =16/25