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 not 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 E₂ = event of getting a non-multiple of 4
Then P(non-multiple of 4) = P(E₂) = 1 - P(multiple of 4)

\[1 - \frac{1}{4} = \frac{3}{4}\]