Chapter 121 Query

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course Mth 152

N/a

If your solution to stated problem does not match the given solution, you should self-critique per instructions at 

http://vhcc2.vhcc.edu/dsmith/geninfo/labrynth_created_fall_05/levl1_22/levl2_81/file3_259.htm.

 

Your solution, attempt at solution. 

 

If you are unable to attempt a solution, give a phrase-by-phrase interpretation of the problem along with a statement of what you do or do not understand about it.  This response should be given, based on the work you did in completing the assignment, before you look at the given solution.

 

006.  Cards

 

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Question:  `q001.  Note that there are 8 questions in this assignment.

 

  Using a standard deck of cards, in how many ways is it possible to get a hand containing exactly two 5's?

 

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Your solution:You would take 2 of the four fives.... no concern for order... and the other three cards would not matter... So, C (4,2) * C (48,3)

confidence rating #$&*:

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Given Solution:  In order to get a hand containing exactly two 5's we must select, without regard for order, two of the four 5's, then we must select the remaining 3 cards from the 48 cards that are not 5's.

 

There are C(4,2) ways to select two 5's from the four 5's in the deck.

 

There are C(48,3) ways to select the 3 remaining cards from the 48 cards which are not 5's.

 

We must do both, so by the Fundamental Counting Principle there are C(4,2) * C(48, 3) ways to obtain exactly two 5's.

 

Self-critique:N/a

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Self-critique rating:3

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Question:  `q002.  Using a standard deck of cards, in how many ways is it possible to get a hand containing exactly two 5's and exactly two 9's?

 

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Your solution: I am just going to give answers from here on out unless I need to explain something: C (4,2) *C (4,2) *C44

confidence rating #$&*:

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Given Solution:  There are C( 4, 2) ways to select exactly two 5's and C(4, 2) ways to select exactly two 9's.  There are 44 remaining cards which are neither 9 nor 5. 

 

The total number of possible ways is therefore C(4, 2) * C(4, 2) * 44.

 

Self-critique:N/a

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Self-critique rating:3

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Question:  `q003.  Using a standard deck of cards, in how many ways is it possible to get a 'full house' consisting of two 5's and three 9's?

 

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Your solution: C (4,2) * C (4,3)

confidence rating #$&*:

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Given Solution:  There are C(4, 2) ways to get two 5's and C(4, 3) ways to get three 9's.  It follows that the number of ways to get the specified 'full house' with two 5's and three 9's is C(4,2) * C(4,3).

 

Self-critique:N/a

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Self-critique rating:3

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Question:  `q004.  Using a standard deck of cards, in how many ways is it possible to get a 'full house' consisting of two 5's and three identical face cards?

 

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Your solution: C (4,2) * C (4,3)

confidence rating #$&*:

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Given Solution:  There are C(4,2) ways to get two 5's and C(4,3) ways to get three of any given face card.  There are 3 possible face cards, so the number of ways to get a 'full house' consisting of two 5's and three identical face cards is 3 * C(4,2) * C(4,3).

 

Self-critique:N/a

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Self-critique rating:3

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Question:  `q005.  Using a standard deck of cards, in how many ways is it possible to get a 'full house' consisting of two of one  denomination and three of another?

 

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Your solution: C (4,2) * C (4,3)

confidence rating #$&*:

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Given Solution:  For any two denominations, e.g., a pair of 5's and three 9's, there are C(4,2) * C(4,3) different full houses.

 

There are 13 possible choices for the pair, which leaves 12 possible choices for the three-of-a-kind, which to by the Fundamental Counting Principle makes 13 * 12 possible choices for the two denominations.  Note that order does matter when choosing the denominations because one has to be the pair and the other the three-of-a-kind.

 

Again by the Fundamental Counting Principle we conclude that there are 13 * 12 * C(4,2) * C(4,3) possible full houses.

 

Self-critique: N/a

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Self-critique rating: 3

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Question:  `q006. Using a standard deck of cards, in how many ways is it possible to get a 'flush' consisting of five cards all of the same suit?

 

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Your solution: C (13,5)

confidence rating #$&*:

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Given Solution:  There are 13 cards in any given suit, so there are C(13,5) hands consisting of all 5 cards in that suit.  There are 4 suits, so there are 4 * C(13,5) possible flushes.

 

Self-critique:n/a

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Self-critique rating:3

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Question:  `q007. Using a standard deck of cards, in how many ways is it possible to get a 'straight' consisting of exactly one each of the denominations 5, 6, 7, 8 and 9?

 

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Your solution: C (4,1) ^5 … I am guessing as it would be C (4,1) * C (4,1) * etc up to 5 times.

confidence rating #$&*:

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Given Solution:  There are four 5's, four 6's, four 7's, four 8's and four 9's.  So there are 4 * 4 * 4 * 4 * 4 = 4^5 possible straights from 5 to 9.

STUDENT QUESTION

 

not sure I understand why is it not C(20,5) 

I bet because it is C(4,1)*C(4,1)…..or 4^5 or maybe not…

INSTRUCTOR RESPONSE

 

There are indeed 20 cards which are 5, 6, 7, 8 or 9, which four of each of the five denominations.

However of the C(20, 5) combinations of 5 of the 20 cards, only a few have one of each denomination. For example, one of the C(20, 5) combinations would be 5 of hearts, 5 of spades, 5 of diamonds, 7 of clubs and 9 of hearts. 

That's not a straight, nor are most of the C(20, 5) combinations of these cards.

C(4,1) * C(4,1) * C(4,1) * C(4,1) * C(4,1) = 4*4*4*4*4 = 4^5, so that is correct. You can check to see that this is a good bit less than C(20, 5).<

Self-critique:COOL! I actually got that right.

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Self-critique rating:3

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Question:  `q008. Using a standard deck of cards, in how many ways is it possible to get a 'straight' consisting of five cards of consecutive denominations, assuming that the 'ace' can be either 'high' or 'low'?

 

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Your solution:Ok, wow... so from the previous question I know that there are 4^5 possibles for straights so if you consider that fact there are 10 possible starting points,,, it would be 10 * 4^5?

confidence rating #$&*:

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Given Solution:  There are 10 possible denominations for the 'low' card of a straight (any card from ace through 10 can serve as the 'low' card of a straight).  There are 4^5 possible straights for each possible low card.  It follows that there are 10 * 4^5 possible straights.

STUDENT QUESTION:  Where does the 4^5 come from? I understand the 10 and 4 different cards of each but did you get the ^5 from the problem before this one?

INSTRUCTOR RESPONSE 4^5 is the number of possibilities for each denomination of the 'low' card. For example we figured out above that there are 4^5 straights with 5 as the low card. 

Similarly there are 4^5 straights with the 'ace' low, another 4^5 with the 2 low, etc., with the 'highest' possible 'low card being 10. So there are 10 possible denominations for the 'low' card, and 4^5 possible straights for each 'low' denomination.

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Self-critique (if necessary):

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Self-critique rating:

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Question:  `q008. Using a standard deck of cards, in how many ways is it possible to get a 'straight' consisting of five cards of consecutive denominations, assuming that the 'ace' can be either 'high' or 'low'?

 

YYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYY

Your solution:Ok, wow... so from the previous question I know that there are 4^5 possibles for straights so if you consider that fact there are 10 possible starting points,,, it would be 10 * 4^5?

confidence rating #$&*:

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Given Solution:  There are 10 possible denominations for the 'low' card of a straight (any card from ace through 10 can serve as the 'low' card of a straight).  There are 4^5 possible straights for each possible low card.  It follows that there are 10 * 4^5 possible straights.

STUDENT QUESTION:  Where does the 4^5 come from? I understand the 10 and 4 different cards of each but did you get the ^5 from the problem before this one?

INSTRUCTOR RESPONSE 4^5 is the number of possibilities for each denomination of the 'low' card. For example we figured out above that there are 4^5 straights with 5 as the low card. 

Similarly there are 4^5 straights with the 'ace' low, another 4^5 with the 2 low, etc., with the 'highest' possible 'low card being 10. So there are 10 possible denominations for the 'low' card, and 4^5 possible straights for each 'low' denomination.

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Self-critique (if necessary):

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Self-critique rating:

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&#Good responses. Let me know if you have questions. &#