posted by Peter .
A ice cream shop sells 4 flavors of ice cream, assume that all orders of two scoops are equally likely, what is the probability that in an order of two scoops both are of the same flavor?
There are 4^2 ways of taking two scoops
Of those, only 4 are both the same
So, 4/16 = .25 is the chance that two random scoops are the same.
Or, you can consider it like this.
Given a first scoop of any flavor, there is a 25% chance that the 2nd scoop is the same, since there are 4 flavors.