Question

A box contains 6 balls numbered from 1 to 6. John pulls a ball from the box, memorizes the number written on the ball and returns the ball in the box. Then Pedro does the same thing: he removes a ball from the box and memorizes the number written on the ball. What is the probability that John took the same number as Peter?

Answer 1

Hello!

As the ball was replaced, the denominator in our probabilities will be the same. As the each had a 1/6 chance of getting the ball with the certain number, we just square the number as they both had the same probability.

1/6·1/6=1/36

There was a 1/36 chance of them selecting the same ball. This is also equivalent to about a 2.8% chance of this event occurring.

I hope this helps!