A = event the card is a heart
B = event the card is a red card
Which of the following is (are) true?
A: P(A or B) = P(A)
B: P(A or B) = P(B)
C: P(A and B) = P(B)
D: P(A and B) = P(A)
Here is the universal set of all 52 cards in the deck:
cards
A♥ 2♥ 3♥ 4♥ 5♥ 6♥ 7♥ 8♥ 9♥ 10♥ J♥ Q♥ K♥
A♦ 2♦ 3♦ 4♦ 5♦ 6♦ 7♦ 8♦ 9♦ 10♦ J♦ Q♦ K♦
A♠ 2♠ 3♠ 4♠ 5♠ 6♠ 7♠ 8♠ 9♠ 10♠ J♠ Q♠ K♠
A♣ 2♣ 3♣ 4♣ 5♣ 6♣ 7♣ 8♣ 9♣ 10♣ J♣ Q♣ K♣
A = event the card is a heart
Here is subset A
A♥ 2♥ 3♥ 4♥ 5♥ 6♥ 7♥ 8♥ 9♥ 10♥ J♥ Q♥ K♥
There are 13 of them out of the 52 cards, therefore
P(A) = 13/52 = 1/4
B = event the card is a red card
Here is subset B
A♥ 2♥ 3♥ 4♥ 5♥ 6♥ 7♥ 8♥ 9♥ 10♥ J♥ Q♥ K♥
A♦ 2♦ 3♦ 4♦ 5♦ 6♦ 7♦ 8♦ 9♦ 10♦ J♦ Q♦ K♦
There are 26 of them out of the 52 cards, therefore
P(B) = 26/52 = 1/2.
P(A or B)
That's the probability that a card is a heart or a red card,
which just means that it is a red card, since hearts are red.
Here is the subset A or B:
A♥ 2♥ 3♥ 4♥ 5♥ 6♥ 7♥ 8♥ 9♥ 10♥ J♥ Q♥ K♥
A♦ 2♦ 3♦ 4♦ 5♦ 6♦ 7♦ 8♦ 9♦ 10♦ J♦ Q♦ K♦
There are 26 of them out of the 52 cards, therefore
P(A or B) = 26/52 = 1/2
P(A or B) is the same as P(B). Therefore B is true.
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P(A and B)
That's the probability that a card is a heart and a red card,
which just means that it is a heart, since hearts are red.
Here is subset A and B:
A♥ 2♥ 3♥ 4♥ 5♥ 6♥ 7♥ 8♥ 9♥ 10♥ J♥ Q♥ K♥
There are 13 of them out of the 52 cards, therefore
P(A and B) = 13/52 = 1/4
P(A and B) is the same as P(A). Therefore D is true.
So B and D are true and A and C are false.
Edwin