Calculate the probability of an event given counts or proportions within a sample space.
64 original probability questions in the SAT Ranker bank, with instant scoring and an Elo-based rank once you sign up. Below are a few free samples with full explanations.
A bag contains marbles in four colours: 6 red, 6 blue, 7 green, and 1 yellow. If one marble is drawn at random, what is the probability that it is NOT blue?
There are 20 marbles total and 6 are blue, so 14 are not blue. Probability = 14/20 = 0.7.
A bag contains 5 red, 3 blue, and 2 green marbles. If one marble is drawn at random, what is the probability that it is NOT blue?
There are 10 marbles total and 3 are blue, so 7 are not blue. Probability = 7/10 = 0.7.
A bag contains marbles in four colours: 40 red, 13 blue, 24 green, and 23 yellow. If one marble is drawn at random, what is the probability that it is NOT red?
There are 100 marbles total and 40 are red, so 60 are not red. Probability = 60/100 = 0.6.
A bag contains marbles in four colours: 20 red, 11 blue, 11 green, and 8 yellow. If one marble is drawn at random, what is the probability that it is NOT red?
There are 50 marbles total and 20 are red, so 30 are not red. Probability = 30/50 = 0.6.
A bag contains marbles in four colours: 4 red, 8 blue, 5 green, and 3 yellow. If one marble is drawn at random, what is the probability that it is NOT green?
There are 20 marbles total and 5 are green, so 15 are not green. Probability = 15/20 = 0.75.