Open Query 21

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course MTH 151

Time of submission: 4:55 PM, 14 January 2012.

001. `Query 1*********************************************

Question: `qQuery 2.1.12 counting #'s 4 to 14

List the elements of the set.

 

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Your solution:

- { 4, 5, 6, 7, 8 , 9, 10, 11, 12, 13, 14}

confidence rating #$&*: 3

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Given Solution:

`a**A list of the elements would just be 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14. **

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Self-critique (if necessary):

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Self-critique Rating:

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Question: `qquery 2.1.24 listing for set of presidents between LBJ and Clinton

 

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Your solution:

- {Nixon, Ford, Carter, Reagan, Bush}

confidence rating #$&*: 3

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Given Solution:

`a** A listing would be {}{}{Lyndon Johnson, Richard Nixon, Gerald Ford, Jimmy Carter, Ronald Regan, George HW Bush, William Clinton}.{}{}Set-builder notation is {x|x is a president who served between Lyndon Johnson and William Clinton}

x is a variable and the condition 'x is a president who served between Lyndon Johnson and William Clinton' tells you what possible things the variable can be.

COMMON ERROR: It's incorrect to say {x | x is the set of presidents who served between Johnson and Clinton}.

x is a president, not a set of presidents. Should be {x|x is a president who served between Lyndon Johnson and William Clinton} **

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Self-critique (if necessary): Given the word “between” the two variables, one would consider that it would exclude said variables. (E.g., in this case, leaving out LBJ and Clinton but including all other presidents within the set) On page 53, under SOLUTION, (a) states, in parentheses, Notice that the word between excludes the endpoint values.)

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Very good.

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Self-critique Rating: 2.5

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Question: `q2.1.40 finite or infinite: set of rat #'s 0 to 1

 

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Your solution: Finite. Given points between 0 to 1, therefore infinite is not a possibility.

confidence rating #$&*: 3

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Given Solution:

`a** Rational numbers have form p/q, where p and q are integers. Numbers like 5/8, 57/31, -3/5, -57843/7843, etc.

The subset {1/2, 1/3, 1/4, 1/5, ... } is just by itself an infinite set of rational numbers between 0 and 1.

Then you have things like 348/937, and 39827389871 / 4982743789, and a whole infinite bunch of others. There are thus infinitely many rational numbers in any interval of the real line.

COMMON MISCONCEPTION: finite, because it doesn't go on forever

Rational numbers have form p/q, where p and q are integers. Numbers like 5/8, 57/31, -3/5, -57843/7843, etc. Not all of these lie between 0 and 1, of course. **

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Self-critique (if necessary): Cleared up the aforementioned misconception. Is this because there can be any value of p/q that makes it infinite?

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Self-critique Rating:

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None of these values are infinite.

But there are uncountably many of them, so the set of all such values is an infinite set.

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Question: `q2.1.48 n(A), A={x|x is a U.S. senator}

What is n(A) and why?

 

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Your solution: 100, because the variable x stands for a single U.S. senator.

confidence rating #$&*: 3

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Given Solution:

`a** n(A) stands for the number of elements in the set--in this case for the number of senators. There are 100, 2 from each State. So n(A) = 100. **

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Self-critique (if necessary):

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Self-critique Rating:

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x does stand for a single senator, but it can take any of 100 different values.

n(A) is the number of different elements in the set A.

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Question: `qquery 2.1.54 {x|x is neagtive number}

 

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Your solution: Well defined.

confidence rating #$&*: 3

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Given Solution:

`a** This notation means all possible values of x such that x is a negative number.

The question is whether the set is well-defined or not.

It is in fact well-defined because there is a definite way to decide whether a given object is an element of the set, because there is a definite way to determine whether an object is a negative number or not.

ALTERNATIVE ANSWER: The set is well-defined because you have a criterion by which you can definitely decide whether something is or is not in the set. **

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Self-critique (if necessary):

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Self-critique Rating:

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Question: `q2.1.74 (formerly 2.1.72) This was not assigned, but you should be able to answer based on your work on similar problems: It is or is it not true that 2 is not not subset of {7,6,5,4}?

 

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Your solution: True.

confidence rating #$&*: 3

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Given Solution:

`a** The statement is that 2 is not a subset. The statement is true because 2 isn't even a set, it's just a number. {2} is a set and could be a subset of something. 2 is just a number; it isn't a set so it can't be a subset of anything.

The usual answer is that 2 isn't a subset because 2 isn't in the set. However that's not the correct reason. The correct reason is that 2 isn't a set and a subset must be a set.

COMMON MISCONCEPTION: the statement says that 2 is not a subset, not that it is not an element of the set. So the reason it's not a subset is that 2 isn't a set at all, so it can't be a subset of anything. **

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Self-critique (if necessary):

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Self-critique Rating:

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Question: `q2.1.86 (formerly 2.1.84). This was not assigned but you did answer several questions related to the sets C={4,10,12}, B={2,4,8,10}, and should be able to answer this.

Is it true or false that every element of C is also an element of B? Be sure to include your reasoning.

 

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Your solution: False

confidence rating #$&*: 3

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Given Solution:

`a** Specifically it's false because the element 12 is in C but not in B. **

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end document

Self-critique (if necessary):

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Self-critique rating:

@&

Each of your last three answers, 'well defined', 'true' and 'false', represents a 50-50 choice between two alternatives.

In such a case it is always necessary to explain the basis for your choice, and on a test it is that explanation, not the choice you actually made, that is graded. (Of course if you made the wrong choice your explanation won't be completely right, but partial credit is often given if the overall reasoning process is sound).

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Question: `q2.1.86 (formerly 2.1.84). This was not assigned but you did answer several questions related to the sets C={4,10,12}, B={2,4,8,10}, and should be able to answer this.

Is it true or false that every element of C is also an element of B? Be sure to include your reasoning.

 

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Your solution: False

confidence rating #$&*: 3

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Given Solution:

`a** Specifically it's false because the element 12 is in C but not in B. **

"

end document

Self-critique (if necessary):

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Self-critique rating:

@&

Each of your last three answers, 'well defined', 'true' and 'false', represents a 50-50 choice between two alternatives.

In such a case it is always necessary to explain the basis for your choice, and on a test it is that explanation, not the choice you actually made, that is graded. (Of course if you made the wrong choice your explanation won't be completely right, but partial credit is often given if the overall reasoning process is sound).

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&#Your work looks good. See my notes. Let me know if you have any questions. &#