Rafi usually eats at one of two fast food venues, choosing BurgerFuel 80% of the
ID: 3307437 • Letter: R
Question
Rafi usually eats at one of two fast food venues, choosing BurgerFuel 80% of the tome and Hungry Jack’s 20% of the time. Regardless of where he goes, he buys a drink on 40% of his visits.
(a) On his next visit to a fast food venue, what is the probability that he goes to BurgerFuel and buys drink?
(b) Are the two events in part (a) independent? Explain your answer.
(c) If Rafi goes to one of the venues and orders a drink, what is the probability that he is at Hungry Jack’s?
(d) What is the probability that Rafi goes to BurgerFuel, or orders a drink, or both?
Explanation / Answer
a) Probability that he goes to BurgerFuel and buys drink is computed as:
= Probability that he goes to BurgerFuel * Probability that he buys drink given that he visits BurgerFuel
= 0.8*0.4
= 0.32
Therefore 0.32 is the required probability here.
b) The 2 events in part a) are independent because the probability that he goes to BurgerFuel and buys drink is computed as the product of the 2 individual probabilities.
c) As the 2 independent are independent, therefore given that he buys a drink at a venue, probability that he is at Hungry Jack’s is computed as the probability that he is at Hungry Jack’s without any condition that is 0.2 here.
Therefore 0.2 is the required probability here.
d) Probability that Rafi goes to BurgerFuel, or orders a drink, or both is computed as:
= Probability that Rafi goes to BurgerFuel + Probability that Rafi goes to Hungry Jack's and orders a drink
= 0.8 + 0.2*0.4
= 0.88
Therefore 0.88 is the required probability here.
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