Question

In a large bag of marbles, 10% of them are red. A child chooses 4 marbles from this bag. If the child chooses the marbles at random, what is the chance that the child gets exactly three red marbles?

Answer 1

the probability of choosing a red marble is equal to it's abundance

P(red)=0.1

Since we dont have quantitative data about how many marbles there are, you would assume that their abundance doesnt change when you take a marble out. We could say they are independent.

P(3 red)=0.1*0.1*0.1*(1-0.1)=\(0.1^3*0.9\)