Drawing a Ball!

Discrete Mathematics Level 3

A bag contains 3 red and 7 black balls. Two balls are selected at random one-by-one without replacement. If the second selected ball happens to be red, what is the probability that the first ball selected is also red?

The above answer in the form of \(\dfrac{a}{b}\), where \(a\) and \(b\) are co-prime positive integers. Submit your answer as \(a + b\)

Excel in math and science

Master concepts by solving fun, challenging problems.

It's hard to learn from lectures and videos

Learn more effectively through short, conceptual quizzes.

Our wiki is made for math and science

Master advanced concepts through explanations, examples, and problems from the community.

Used and loved by 4 million people

Learn from a vibrant community of students and enthusiasts, including olympiad champions, researchers, and professionals.