Question

20 cards are numbered from 1 to 20. One card is drawn at random. What is the probability that the number on the cards is a multiple of 4?

Answer 1

Clearly, the sample space is given by S = {1, 2, 3, 4, 5........19, 20}.
i.e. n(S) = 20

Let E₁ = event of getting a multiple of 4
Then E₁ = {4, 8, 12, 16, 20}
i.e. n(E₁) = 5
Hence, required probability = P(E₁) = \[\frac{n\left( E_1 \right)}{n\left( S \right)} = \frac{5}{20} = \frac{1}{4}\]