You select a marble without looking and then put it back. If you do this 5 times, what is the best prediction possible for the number of times you will pick a pink marble?

Answer:
You have a chance to get the pink marble at least once.
Since the ratio of pink marbles to other marbles is 1:5 meaning only 1 pink marble for every five you pick usually, the number of times you might pick a pink marble is 1 if you did it 5 times.