Probability

Compound Probability

So far, we have worked with probabilities involving one specific desired outcome. Now you will investigate probabilities of compound events. Compound events are events with combinations of outcomes.

When we want to find the compound probability that EITHER one of the outcomes OR the other is desired:

• Add the desired outcomes together

• See if we can simplify

Either/Or Probability

Either/or probability refers to the probability that one event or the other will occur. For example, what is the probability that you will draw a Jack or a three from a normal deck of cards? Or, what is the probability that you will roll a 3 or a 5 when rolling a normal 6-sided die? To solve this type of probability problem, here is the formula you will use:

P(A or B) = P(A) + P(B)

Multiple Choice

If you were to spin the spinner at left, what would be the probability of landing on green or purple?

• 1/4

• 3/4

• 2/3

• other

Multiple Choice

What is the probability of getting either blue or green on a spinner that is 3/10 green and 1/5 blue?

• 2/5

• 4/15

• 1/2

• other

Multiple Choice

What is the probability you roll a 1 or a 6 on a standard dice?

• 1/3

• 2/3

• 1/6

• other

Poll

I can solve either/or probability problems

• Yes, I can

• Sort of

• Not at all