Let A be the event that you go to the mall after class Let B

Let A be the event that you go to the mall after class. Let B be the event that you meet friends for coffee after class. The probability that you go to the mall after class is 0.4, and the probability that you meet friends for coffee after class is 0.25. Assume that whether you go to the mall after class has no effect on wheter you meet friends for coffee.

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a) What is the probability that you go to the mall AND meet friends for coffee?

b) What is the probability that you go the the mall OR meet friends for coffee?

c) What is the probability that you go to the mall, GIVEN that you meet friends for coffee?

Solution

Let A be the event that you go to the mall after class. Let B be the event that you meet friends for coffee after class. The probability that you go to the mall after class is 0.4, and the probability that you meet friends for coffee after class is 0.25. Assume that whether you go to the mall after class has no effect on wheter you meet friends for coffee.

SHOW ALL WORK INCLUDING FORMULAS IF USED

Event A= go to mall

Event B=meet friend

P( A) =0.4

P(B) =0.25

A and B are independent

P( A and B) = P( A)*P(B) = 0.4*0.25 =0.1

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

=0.4+0.25-0.1 =0.55

c) What is the probability that you go to the mall, GIVEN that you meet friends for coffee?

P( A/B) = P( A and B)/ P(B) = 0.1/0.25 =0.4