Find the probability that a number selected from numbers 1, 2, 3…

Find the probability that a number selected from numbers 1, 2, 3,..., 20 is a prime number, when each of the given numbers is equally likely to be selected?

This problem repeats another one in the library (at most with different numbers), so it's left out of browsing.

AQuA-RAT — Algebra Question Answering with Rationales (Ling et al., DeepMind, 2017) · train #16292