HMa10 Sannolikhet

Homework for 9c for Wednesday May 22, 2019.

A bag contains 2 blue balls and 3 green balls.

Pete takes a ball at random from the bag, records its colour and replaces it.
He does this two more times.

Work out the probability that, of the three balls Pete takes, exactly two are the same colour.
(Hint – what is the alternative to 2 being the same colour?)