What is the probability tht a randomly chosen two digit integer is a multiple of 3?

Explanation

2-digit positive integers are 10, 11, 12, ...., 98, 99.
These are 90 numbers out of which one number can be chosen in 90 ways.

Therefore,
Total number of elementary events = 90.


Out of these 90 numbers, 30 numbers (12, 15, 18, ..., 96, 99) are multiples of 3.
One number out of these 30 numbers can be chosen in 30 ways.

Therefore, favourable number of elementary events = 30.


Hence, required probability = 30/90=1/3​