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.
002. `Query 2
Question: `q2.2.24 U={a,b,...,g}, A={a,e}, B={a,b,e,f,g}, C={b,f,g}, D={d,e}
Is the statement 'C is not a proper subset of U' true or false and why?
Your solution:
Confidence Assessment:
Given Solution:
`a** The statement is false.
C is a proper subset of U because all elements of C are in the universal set, and because there are elements of U that aren't in C. Note that it takes both of these conditions to make U a proper subset of C, since a proper subset cannot be identical to other set. **
Self-critique (if necessary):
Self-critique Rating:
Question: `qQuery 2.2.30 phi s D
Your solution:
Confidence Assessment:
Given Solution:
`a** Note that You should be responding to problem 2.2.30 from the homework you worked out on paper. The shorthand notation is for my reference and won't always make sense to you. For clarification, though, the symbol for the empty set is the Greek letter phi.
One set is a subset of another if every element of that set is in the other. To show that a set isn't a subset of another you have to show something in that set that isn't in the other.
There's nothing in the empty set so you can never do this--you can never show that it has something the other set doesn't. So you can never say that the empty set isn't a subset of another set.
Thus the empty set is a subset of any given set, and in particular it's a subset of D.
ALTERNATIVE ANSWER: As the text tells you, the empty set is a subset of every set.
ANOTHER ALTERNATIVE
Every element of the empty set is in D because there is no element in the empty set available to lie outside of D.
ONE MORE ALTERNATIVE: The empty set is a subset of every set. Any element in an empty set is in any set, since there's nothing in the empty set to contradict that statement. **
Self-critique (if necessary):
Self-critique Rating:
Question: `q(2.2.31, previously 2.2.33)
Is the following statement true or false:
D is not a subset of B
Is the statement true or false and why?
Your solution:
Confidence Assessment:
Given Solution:
`a** D is a subset of B if every element of D is an element of B-i.e., if D doesn't contain anything that B doesn't also contain.
The statement says that D is not a subset of B. This will be so if D contains at least one element that B doesn't. **
Self-critique (if necessary):
Self-critique Rating:
Question: `q2.2.34 (previously 2.2.36) there are exactly 31 subsets of B
Your solution:
Confidence Assessment:
Given Solution:
`a** If a set has n elements then is has 2^n subsets, all but one of which are proper subsets. B has 5 elements so it has 2^5 = 32 subsets. So the statement is false.
There are exactly 31 proper subsets of B, but there are 32 subsets of B. **
Self-critique (if necessary):
Self-critique Rating:
Question: `qQuery 2.2.38
Is the statement true or false and why?
There are exactly 128 proper subsets of U
Your solution:
Confidence Assessment:
Given Solution:
`a** The set is not a proper subset of itself, and the set itself is contained in the 2^n = 2^7 = 128 subsets of this 7-element set. This leaves 128-1 = 127 proper subsets.
So thre are not 128 proper subsets of this set.**
Self-critique (if necessary):
Self-critique Rating:
Question: `qQuery 2.2.45 U={1,2,...,10}. What is the complement of {1, 2, 3, 4, 6, 8}?
(previously 2.2.48 complement of {2,5,7,9,10} )
What is the complement of the given set?
Your solution:
Confidence Assessment:
Given Solution:
`a** the complement is {1,2,3,4,6,8}, the set of all elements in U that aren't in the given set.
The elements 5, 7, 9and 10 are not in the given set but are in U, so the complement is the set
{5, 7, 9, 10}**
Self-critique (if necessary):
Self-critique Rating:
Question: `qquery 2.2.59 in how many ways can 3 of the five people A, B, C, D, E gather in a suite?
Your solution:
Confidence Assessment:
Given Solution:
`a** The answer here would consist of a list of all 3-element subsets: {a,b,c}, {a,b,d}, {a,b,e}, {a,c,d} etc. There are ten such subsets.
Using a,b,c,d,e to stand for the names, we can list them in alphabetical order:
{a,b,c), {a,b,d}, {a,b,e}, {a,c,d}, {a,c,e}, {a,d,e|, {b,c,d}, {b,c,e}, {b,d,e}, {c, d, e}**
Question: `q (previously 2.1.74) (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}?
<p> </p>
Your solution:
Confidence Assessment:
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. **
Self-critique (if necessary):
Self-critique Rating:
Question: `q (previously 2.1.86) (formerly 2.1.84). This was not assigned but you should be able to answer this.
If C={4,10,12} and B={2,4,8,10}:
Is it true or false that every element of C is also an element of B? Be sure to include your reasoning.
<p> </p>
Your solution:
Confidence Assessment:
Given Solution:
`a** Specifically it's false because the element 12 is in C but not in B. **