Problema Solution
We have a box with 8 green marbles, 5 red marbles, and 7 blue marbles. We choose 3 marbles from the box at random without looking.
What is the probability they will all be green?
Answer provided by our tutors
P(all 3 marbles are green) = (8/20)*(7/19)*(6/18)
P(all 3 marbles are green) = (2*7)/(3*5*19)
P(all 3 marbles are green) = 0.0491
Second way to calculate this probability is using the formula for combinations
P(all 3 marbles are green) = C(8, 3) / C(20, 3)
P(all 3 marbles are green) = (8!/(3! 5!)) / (20!/(3! 17!))
P(all 3 marbles are green) = 0.0491