A number is chosen at random from 10 to 30 both inclusive. What is the probability that the number is divisible by 3?

A number is chosen at random from 10 to 30 both inclusive. What is the probability that the number is divisible by 3?

Answer Details

Sample space S = {10, 11, 12, ... 30}
Let E denote the event of choosing a number divisible by 3
Then E = {12, 15, 18, 21, 24, 27, 30} and n(E) = 7
Prob (E) = $\frac{n\left(E\right)}{n\left(E\right)}$
Prob (E) = $\frac{7}{21}$
Prob (E) = $\frac{1}{3}$