Problem 22
a)
The face cards are Jack, Queen, King. We have four copies of each.
There are 3*4 = 12 face cards total.
12/52 represents the probability of picking a face card.
4/52 represents the probability of picking an ace, since we have 4 aces out of 52 cards. We don't drop to 51 since we put the first card back.
Multiplying the fractions gives (12/52)*(4/52) = 48/2704 = 3/169
Answer: 3/169
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b)
We do the same steps as before, but the 4/52 will be changed to 4/51. This is because the first card is not put back.
(12/52)*(4/51) = 48/2652 = 4/221
Answer: 4/221
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Problem 23
a)
4/52 represents the probability of picking a '2', and it also represents the probability of picking a '10' if we put the first card back
(4/52)*(4/52) = 16/2704 = 1/169
Answer: 1/169
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b)
We'll change the second instance of 4/52 into 4/51 because that first card isn't put back
(4/52)*(4/51) = 16/2652 = 4/663
Answer: 4/663
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Problem 24
a)
4/52 = probability of picking an ace
12/52 = probability of picking a face card
4/52 = probability of picking '7'
Each denominator is 52 because we are putting the cards back
(4/52)*(12/52)*(4/52) = 192/140608 = 3/2197
Answer: 3/2197
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b)
We do the same thing as before, but we decrease the denominator by 1 each time we pull out another card
(4/52)*(12/51)*(4/50) = 192/132600 = 8/5525
Answer: 8/5525
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Problem 25
a)
The probability of picking a king is 4/52. This is the same whether we're on the first king, second or third. This is because we're putting the card back.
(4/52)*(4/52)*(4/52) = 64/140608 = 1/2197
Answer: 1/2197
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b)
Now that the cards aren't put back, we'll have the denominators drop by 1 each time (52,51,50)
So the probability is
(4/52)*(4/51)*(4/50) = 64/132600 = 8/16575
Answer: 8/16575