Question

There are 30 cards of same size in a bag, on which numbers 1 to 30 are written. One card is taken out of the bag at random. Find the probability that the number on the selected card is not divisible by 3.

Answer 1

Total no. of possible outcomes = 30 {1, 2, 3, ... 30}

E ⟶ event of getting no. divisible by 3.

No. of favourable outcomes = 10 {3, 6, 9, 12, 15, 18, 21, 24, 27, 30}

Probability, P(E) =`"No. of favorable outcomes"/"Total no. of possible outcomes"`

P(E) = `10/30`

= `1/3`

`barE`⟶ event of getting no. not divisible by 3.

`P(barE) = 1 - P(E)`

= `1 - 1/3` 

= `2/3`