Question

A box contains 20 cards numbered from 1 to 20. A card is drawn at random from the box. Find the probability that the number on the drawn card is a prime number   

Answer 1

Total number of outcomes = 20 

The prime numbers from 1 to 20 are 2, 3, 5, 7, 11, 13, 17 and 19.
So, the favourable number of outcomes are 8.
∴ P(number on the drawn card is a prime number) = \[\frac{\text{ Favourable number of outcomes }}{\text{ Total number of outcomes }} = \frac{8}{20} = \frac{2}{5}\]