NECO 2023 · Paper 1 · Q50

What is the probability that an integer selected from $\{1, 2, 3, \dots, 29, 30\}$ is a prime number?

Worked solution (try it first)

There are 30 numbers to choose from.
The primes up to 30 are 2, 3, 5, 7, 11, 13, 17, 19, 23, 29, which is 10 numbers.
So the probability is $\frac{10}{30} = \frac13$ , option E.