SOLUTION: I need someone to double check my answer. One card is slected at random from a ordinary set of 52 cards. Find the probability of each of the following events: a spade and a 5

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Question 171510This question is from textbook
: I need someone to double check my answer.
One card is slected at random from a ordinary set of 52 cards. Find the probability of each of the following events: a spade and a 5 are drawn
4 fives = heart, diamond, clover and spade
14 spades - 1(5 of spades) = 13 spades
4/52 = 1/13
13/13 = 1
I came up with answer of 1%
This question is from textbook

Found 2 solutions by Mathtut, solver91311:
Answer by Mathtut(3670) About Me  (Show Source):
You can put this solution on YOUR website!
can you restate the problem it is unclear......one card is drawn according to the instructions.... then you say a spade and a 5. Is the question what is the probability that the 5 of spades is drawn???

Answer by solver91311(12126) About Me  (Show Source):
You can put this solution on YOUR website!
First of all, the statement describing the experiment is ambiguous. Are you drawing one card and it must be exactly the 5 of spades, or are you drawing two cards, one of which must be a 5 and the other must be a spade? Furthermore, you don't specify if, on a two card draw, whether you are replacing the first card before making the second draw.

Case 1: One card draw and success = 5 of spades. Trivial. There is only one 5 of spades in the deck, so your probability is 1%2F52

Case 2: Two card draw with replacement and success = one card will be a spade of any rank and the other will be a 5 of any suit.
First of all, there are 13 spades out of 52 cards, so the probability of drawing any spade is 13%2F52.

Second, there are four 5s in the deck, so the probability of drawing a 5 is 4%2F52

And the total probability is the product 13%2F52%2A4%2F52=52%2F2704, approximately 0.019 or 1.9%

Case 3: Two card draw WITHOUT replacement and success is the same as Case 2.

You have to consider the possibility that the first card drawn is the 5 of spades. So:

Case 3a: The probability of drawing a spade other than the 5 times the probability of drawing a 5 when the deck is one card smaller 12%2F52%2A4%2F51

Plus

Case 3b: The probability of drawing the 5 of spades times the probability of drawing a 5 with a deck that is one card smaller AND has one less 5 1%2F52%2A3%2F51

Total probability %2812%2F52%2A4%2F51%29%2B%281%2F52%2A3%2F51%29 roughly the same value as Case 2.

Case 4: You really meant to ask "What is the probability, on a one card draw, that the card will be a spade OR a 5"

Again 13 spades and 4 fives one of which is a spade and already counted, so there are 3 other suited fives, making a total of 16 cards that represent a successful experiment, and your probability is 16%2F52 (You could also look at it as 4 fives and 12 spades that aren't a five adding up to the same 16 successes out of 52 possibilities.)