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  #1  
Old 01-28-2018, 04:24 PM
ubhutto ubhutto is offline
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Default Simple Probability Problem

Hi Everyone

I had a relatively simple problem that for some reason i can't get my head around.

The problem states:

If two cards are drawn from a deck then what is the chances that the sum of the two is 21?

face card = 10
ace = 11

I got the solution but i just don't understand how they did it. can someone explain it to me.

Thank you in advance for your help.
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  #2  
Old 01-28-2018, 05:55 PM
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Marcie Marcie is online now
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Quote:
Originally Posted by ubhutto View Post
Hi Everyone

I had a relatively simple problem that for some reason i can't get my head around.

The problem states:

If two cards are drawn from a deck then what is the chances that the sum of the two is 21?

face card = 10
ace = 11

I got the solution but i just don't understand how they did it. can someone explain it to me.

Thank you in advance for your help.
How did you get the solution?

They probably did something similar.
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  #3  
Old 01-28-2018, 06:06 PM
ubhutto ubhutto is offline
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Quote:
Originally Posted by Marcie View Post
How did you get the solution?

They probably did something similar.
They just gave a number but not how to get to it, any idea how to work it out?
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Old 01-28-2018, 07:15 PM
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Marcie Marcie is online now
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Quote:
Originally Posted by ubhutto View Post
They just gave a number but not how to get to it, any idea how to work it out?
Very carefully?
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Old 01-28-2018, 07:26 PM
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Marcie Marcie is online now
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Originally Posted by ubhutto View Post
They just gave a number but not how to get to it, any idea how to work it out?
Is the answer about 4.83%? (i.e 32/663)

If so, then yes. If not, I need to review my probability.
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Old 01-28-2018, 07:45 PM
royevans royevans is offline
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There are 12 face cards (4 jacks, 4 kings, 4 queens) and 4 aces and 4 10's.

Number of pairs involving those above combinations is (16*4) * 2 = 128.
Number of total two card combinations = 52 * 51 = 2652

Pr(sum = 21) = 128/2652= 0.04827?

Oh boy...
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Old 01-28-2018, 09:20 PM
Academic Actuary Academic Actuary is online now
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Alternatively there are two sequences (10,11) and (11,10). Sum the two probabilities.
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