PROBABILITY
Probability expresses the likelihood of an event occurring. It is a number between 0 and 1 – a probability of 0 means it is impossible while a probability of 1 means it is certain.
P(event) =
EX: P(head) = P(heart) =
EX: In one toss of a die, what is the probability of each event?
a. rolling a 5 b. rolling an odd number
c. rolling a number less than 7 d. rolling a 7
EX: One card is drawn at random from an ordinary deck of 52 cards. Find the probability of each event.
a. a red face card b. 6 of clubs
c. a king d. not a king
A sample space is a listing of all the possible outcomes. For a family with 3 children, the sample space of the outcomes (boy or girl) is shown below.
1st child B G
2nd child B G B G
3rd child B G B G B G B G
1. A number wheel is divided in 12 equal sectors, numbered 1 – 12. Find the probability of each event.
a. It is a 5 b. It is a 2-digit number
c. It is a factor of 12 d. It is an odd number
e. It is a negative number f. It is a 3 or a 6 or a 9
2. A letter is selected at random from those in the word RECTANGLE. Find the probability of each event.
a. It is a vowel b. It is a consonant
c. It is between D and M in the alphabet d. It is either C or G
3. One marble is drawn at random from a bag containing 2 red, 4 yellow, and 6 blue marbles. Find the probability of each event.
a. It is yellow b. It is blue
c. it is not yellow d. It is red or blue
4. One card is drawn at random from a 52-card deck. Find the probability of each event.
a. It is a king b. It is a club
c. It is red d. It is the ace of spades
e. It is a red jack f. It is red or black
g. P(not a 2) h. P(not a diamond)
5. Make a sample space for tossing three coins.
Then find:
P(3 tails) P(1 tail) P( 2H and 1T)