HELP! GEOMETRY MATH WORK! PROBABILITY!

Question

A test consists of nine true/false questions. A student who forgot to study guesses randomly on every question. What is the probability that the student answers at least two questions correctly?

Answer 1

This is a binomial probability problem

The probability of at least 2 questions correct is 1 minus the probability of 0 or 1.

1 - {₉C_{0 + 9}C₁]2^-9 = 1 - (10/2⁹)