36Probability of one outcome
A bag has 5 red, 3 blue and 2 green marbles. One marble is picked at random. What is the probability it is blue?
The probability of picking blue is 3/10. There are 10 marbles in total (5+3+2) and 3 of them are blue, so P(blue) = 3/10. Check: 5/10 + 3/10 + 2/10 = 1, confirming the totals work.