# How to Calculate Probability of Obtaining Unknown Questions

Probability is a branch of Mathematics that deals with predicting the likelihood of different outcomes. In this case, we are looking at the probability of a student getting at least one question in a ticket that they do not know.

To calculate this probability, we need to consider the complementary event - the probability of the student knowing all the questions in the ticket. Given that the student knows 20 questions out of a total of 24, and the ticket contains 3 questions, we can calculate the probability as follows:

- Total combinations of questions in a ticket of 3 out of 24: ${24 \choose 3}$
- Combinations of questions the student knows: ${20 \choose 3}$

Therefore, the probability of knowing all questions in the ticket is ${20 \choose 3}/{24 \choose 3}$. To find the probability of getting at least one unknown question, we subtract the probability of knowing all questions from 1.

By performing the calculations, we arrive at the probability of 0.917 or 91.7%, which indicates the likelihood of the student encountering at least one unfamiliar question in the ticket.