Question

A number between 30 and 50 is chosen at random. What's the probability that the number contains at least one 4

Answer 1

11/21

Explanation:

34 and the 10 numbers in the 40s have at least one 4. If you include 30 and 50 in the range you're choosing from, then 11 out of the 21 numbers have at least one 4.

A randomly chosen integer from [30, 50] has a probability of 11/21 of having at least one 4.