Probability Rules and Addition Rules

The weather forecaster predicted it will be 4/5 chance of rain for Monday and 2/3 chance of rain for Tuesday. What is the probability it will rain both days?

• 1/2

• 20/15

• 8/15

• 6/8

Given P(A) = .8 and P( B| A) = .3, find P( A and B).

• 2.6

• .12

• .24

• .38

An event has a 1/4 chance of occurring. What is the chance of it not occurring?

• 3/4

• 1/4

• Can't find with this information

• .14

Event A has a 1/2 chance of occurring, Event B has a 1/2 Chance of occurring and they have a 1/4 chance of happening at the same time. What is the probability of Event A or Event B happening?

• 1

• 1/2

• 1/4

• 3/4

Answer explanation

You use the Addition rule of Non-ME Events

P(A or B)=P(A)+P(B)-P(A and B)

Two events are (a)   if they cannot happen at the same time

Event A has a 5% chance of occurring, what is the chance of it NOT occurring?

• 50%

• 95%

• 90%

• 15%

To find the probability of Event A OR Event B happening, what rule do we use?

• Addition Rule

• Multiplication Rule

• Complement Rule

• Subtraction Rule

If we have non-mutually exclusive events, how does the addition rule change?

• There is a part we have to multiply

• There is a part we ahve to divide

• There is an extra added part

• There is an extra subtracted part

If event A has a 1/4 chance of happening, event B has a 2/4 chance of happening, and there is a 1/3 chance that they Both happen. What is the probability of Event A or Event B happening?

• 5/12

• 2/4

• 3/4

• 12/5

What is the probability of rolling a fair, six-sided die twice and rolling an even number or a 3?

• 1/6

• 2/3

• 4/6

• 1/2