Problem 1
Answer: 7/10
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Explanation:
The formula we'll use is
P(A or B) = P(A) + P(B)
which only works if A and B are mutually exclusive events.
P(A or B) = P(A) + P(B)
P(A or B) = 7/20 + 7/20
P(A or B) = (7+7)/20
P(A or B) = 14/20
P(A or B) = (7*2)/(10*2)
P(A or B) = 7/10
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Problem 2
Answer: 3/4
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Explanation:
We'll use the same formula as the previous problem.
P(A or B) = P(A) + P(B)
P(A or B) = 3/10 + 9/20
P(A or B) = 6/20 + 9/20
P(A or B) = (6+9)/20
P(A or B) = 15/20
P(A or B) = (3*5)/(4*5)
P(A or B) = 3/4
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Problem 3
Answer: 3/5
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Explanation:
We'll use the same formula as the previous problem.
P(A or B) = P(A) + P(B)
P(A or B) = 7/20 + 1/4
P(A or B) = 7/20 + 5/20
P(A or B) = (7+5)/20
P(A or B) = 12/20
P(A or B) = (4*3)/(4*5)
P(A or B) = 3/5
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Problem 4
Answer: 0
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Explanation:
This time we're asked to find P(A and B), but since the two events are mutually exclusive, this means the probability of both occurring is 0.
Mutually exclusive events cannot happen simultaneously.
An example would be flipping heads and tails at the same time on the same coin.
The info about P(A) and P(B) is not relevant.
