Terms
The likelihood that an event will occur.
Probability
You roll a fair die. What is the probability of rolling a number greater than 5.
1/6 = 17%
You flip a coin and roll a fair die. What is the probability of the coin landing heads up and the die landing on an even number?
1/2 ・ 3/6 = 3/12 = 25%
A fair die is rolled. Find the probability of rolling a 4 or a 5.
1/6 + 1/6 = 1/3 = 33%
A spinner has 12 equal-sized sections number 1 to 12. Find the probability of landing on a 3 or a 4.
1/12 + 1/12 = 1/6 = 17%
The occurrence of one event does not affect the probability of occurrence of the other event.
Independent Probability
The probability of picking a green crayon from a box that contains: 2 red, 3 blue, 4 green and 1 yellow.
2/5 = 40%
You roll a fair die twice. What is the probability that the first roll lands on a 5 and the second roll lands on 6?
1/6・1/6 = 1/36 = 2.7%
A fair die is rolled. Find the probability of rolling multiples of 2 or multiples of 3.
(3/6 + 2/6) - 1/6 = 4/6 = 67%
A spinner has 12 equal-sized sections number 1 to 12. Find the probability of landing on an odd number or a multiple of 5.
(5/12 + 2/12) - 1/12 = 6/12 = 1/2 = 50%
The occurrence of one event does affect the probability of the occurrence of the other event.
Dependent Probability
The probability of rolling an odd number on a fair die.
1/2 = 50%
A box contains 3 red marbles, 2 white marbles, 4 blue marbles and 3 green marbles. Find the probability of selecting a green marble on the second draw if the first marble is blue.
1/11 = 9%
P(A) = 3/10 P(B) = 1/2 Find P(A or B).
3/10 + 5/10 = 8/10 = 80%
You roll a red number die and a blue number die. Find the probability of rolling a red greater than 2 and then a blue 4.
4/6 ・ 1/6 = 4/36 = 11%
Two events that can happen at the same time.
Inclusive
The probability of picking a Diet Coke out of a cooler that contains: 6 Coke, 3 Sprite, 4 Diet Coke, 7 waters, and 2 Dr. Pepper.
2/11 = 18%
There are 10, well-shuffled cards, numbered 1-10 in a box. Three cards are drawn without replacement. If the numbers on the first and second cards are 4 and 6 respectively, find the probability of selecting an even number on the third one.
3/8 = 37.5%
P(A) = 1/4 P(B) = 13/20. If A and B are mutually exclusive, find P(A or B).
5/20 + 13/20 = 18/20 = 90%
A bag contains 2 tiles with "x", 6 tiles with "y", and 4 tiles with "z". You pick a second without replacing the first. What is the probability of picking a "y" then an "x"?
6/12 ・ 2/11 = 12/132 = 9%
The likeliness of 2 independent events occurring. It is equal to the probability of the first event multiplied by the probability of the second event.
Compound Probability
A spinner has (3) 4's, (2) 8's, (5) 9's and (3) 10's. What is the probability that the spinner will land on a 6?
0/13 = 0%
There are 10 cards in a box, numbered from 1 to 10. The cards are shuffled and drawn at random. If 2 cards are drawn without replacement, find the probability of drawing a 4 or a 5 on the first draw and any even prime number on the second draw.
2/10 ・ 1/9 = 1/45 = 2%
A box contains 3 red cards, numbered 1 to 3. It also contains 5 black cards, numbered 1 to 5. You randomly pick a card. What is the probability that it is black or has and odd number.
(5/8 + 5/8) - 3/8 = 7/8 = 87.5%
There are 12 girls and 14 boys in class. The teacher puts the names of the students in a hat and randomly picks one name. Then the teacher picks another name without replacing the first. What is the probability that both students that are picked are boys?
14/26 ・ 13/25 = 182/650 = 28%