Question

A box contains 6 red marbles numbered 1 through 6 and 4 white marbles numbered from 12 through 15. Find the probability that a marble drawn is white and odd numbered .

Answer 1

Total number of marbles = (6 + 4) = 10
Let S be the sample space.
Then n(S) = number of ways of selecting one marble out of 10 = ¹⁰C₁ = 10 ways

Let E₂ = event of getting a white marble, which is odd numbered.
i.e. E₂ = {13, 15}
∴  n(E₂) = 2
Hence, required probability = \[\frac{n\left( E_2 \right)}{n\left( S \right)} = \frac{2}{10} = \frac{1}{5}\]