Basic Probability
What is the probability of flipping a coin and getting tails?
0.5 or 1/2
You recently took a poll of 100 people at the high school to find out the most popular color. You found out that 24 people chose blue. What is the relative frequency of the color blue?
6/25 or .24
How many ways are there to arrange 7 people in this class for a photo?
7! = 5040
You select a muffin from a bag containing 50 muffins. There are 18 blueberry, 13 lemon poppyseed, 11 chocolate chip, and 8 cinnamon sugar. What is the probability that you select a cinnamon sugar or blueberry muffin?
13/25 or .52
In a survey of students, 54% have a sister, 35% have a brother, and 20% have both a brother and sister. What is the probability that a randomly selected student will have a brother given that they have a sister.
P(both)/P(sister)= .2/.54= .37 or 37%
You select a muffin from a bag containing 50 muffins. There are 18 blueberry, 13 lemon poppyseed, 11 chocolate chip, and 8 cinnamon sugar. What is the probability that you select a cinnamon sugar muffin?
4/25 or .16
You are choosing marbles from a bag with green marbles and red marbles. You select 2 marbles at a time and repeat the experiment 30 times. Here are the results:
GG occurred 4 times
GR occurred 11 times
RG occurred 13 times
RR occurred 2 times
If two more marbles are chosen at random, what's the probability of choosing exactly one green marble?
0.8 or 4/5
You are at Flub's and they have a deal where you can choose 4 toppings for your make-your-own cyclone. There are 20 toppings to choose from, how many different kinds of cyclones could you create?
COMBINATION- 4845
What's the probability rolling a 5 on a number cube and flipping a coin and getting tails?
1/6 times 1/2 = 1/12 or .083
In a survey of students, 54% have a sister, 35% have a brother, and 20% have both a brother and sister. What is the probability that a randomly selected student that has a brother will also have a sister?
P(both)/P(brother)= .2/.35 = .57 or 57%
You select a card labeled 1-15. What is the probability that you select a card less than 5?
4/15 or .267
In this class, I am selecting three people for very important jobs. One of the jobs is keeping track of calculators, another is making sure the door stays locked, and the last is keeping the plants watered. How many ways are there to select the people for these three positions if there are 20 people in the class?
PERMUTATION- 6840
I am randomly handing out Smarties and lollipops to students doing their work. There are 50 smarties and 25 lollipops. What is the probability that the first piece of candy I hand out is a smartie and the second is a lollipop?
50/75 times 25/74= 25/111 or 0.225
60% of students studied for their test while 40% did not. 70% of students passed their test. 90% of the people that studied passed. Make a two-way frequency table with this information. Then, what is the probability that a student passed the test given that they did not study?
16/40 or 2/5 or 0.4
You roll a number cube 12 times. Here are the results: {4, 2, 5, 2, 1, 2, 4, 6, 3, 3, 1, 5}. What is the experimental probability of rolling a number greater than 3?
5/12 or .4167
Four cards are randomly chosen from a set numbered from 1 to 20. What is the probability that the chosen cards are numbered 4, 6, 7, and 15?
1/(15C3) or 1/455
My desk contains lots of different color pens. There are 10 black pens, 15 blue pens, 4 red pens, and 1 pink pen. What is the probability that you select a red pen and then without replacing select a black pen?
4/30 times 10/29= .045977 or 4/87
60% of students studied for their test while 40% did not. 70% of students passed their test. 90% of the people that studied passed. Make a two-way frequency table with this information. Then, what is the probability that a student studied given that they failed the test?
6/30 or 1/5 or .2
60% of students studied for their test while 40% did not. 70% of students passed their test. 90% of the people that studied passed. Make a two-way frequency table with this information. Then, what is the probability that a student failed and did not study?
24/100 or .24