BASIC PROBABILITY:
o There are three ways to help solve basic probability situations:
 LIST: Simply list all of the possible things that could occur. Do this systemically so as not
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to forget any possible outcomes. Not great for many outcomes.
TREE: This is a great method when there are several events that occur, like the coin
problems. Again, this is not great if there are many possible outcomes.
AREA: This is an excellent method but is only effective when there are TWO independent
events that occur. For example, pick a marble then roll the dice.
Answer the following questions using one of the above methods.
1) First you spin spinner #1. Then you spin spinner #2.
SPINNER #1
SPINNER #2
a. Make a tree diagram to represent this
situation.
A (1/3)
U (1/6)
T (1/4)
I (1/2)
F (3/4)
b. Make an area diagram to represent this situation.
c. What is the probability of making the word “IF?”
d. Using only real English words, what is the probability of making a word?
e. Suppose the game costs $5 to play. If you win, you win $8. Should you play this
game? Why or why not? Use the expected value of the game to help make your
decision.
2) In a casino game involving two dice, you win if you roll a 7 or 11 on the first roll.
a. Make an area diagram for rolling two dice.
b. What is the probability of winning?
3) A Roulette wheel has 38 slots with numbers. The numbers are 00,0,1,2,3,4,5,6,7, … all the way
to 36. Numbers 1-18 are RED. Numbers 19-36 are BLACK. Numbers 0 and 00 are GREEN.
a. Suppose the player plays the game twice. Make an area diagram for playing Roulette
twice.
b. What is the probability of getting RED the first time AND RED the second time?
c. Suppose the player bet $250 that she would get RED-RED. If she wins, she gets $1000.
Is this a smart bet? Explain using the idea of expected value.
4) Harold sorted his jellybeans into two jars. Jar 1 has 6 black and 4 purple jellybeans. Jar 2 has 3
yellow, 5 orange, and 2 white jellybeans.
a. Make an area diagram for randomly picking one jellybean from each jar.
b. What is the probability of getting 1 black and 1 orange?