Understanding Sets: Definitions and Examples
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Questions and Answers

Which of the following collections would be considered a well-defined set?

  • The set of all difficult math problems.
  • The set of all attractive people living in London
  • The set of the best songs ever recorded.
  • The set of all students enrolled in exactly one IT course at Harvard University in 2024 (correct)

If set A = {2, 4, 6, 8} and set B = {even numbers less than 10}, which statement is correct?

  • Set A and Set B both contain an infinite amount of elements
  • Set A is not equal to set B because they are described differently.
  • Set A is a subset of set B, but not equal.
  • Set A is equal to set B because they contain exactly the same elements. (correct)

Given a universal set U = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10} and a set A = {2, 4, 6, 8}, which elements of U are NOT elements of A?

  • {1, 3, 5, 7, 9} (correct)
  • {9, 10}
  • {2, 4, 6, 8}
  • {1, 2, 3, 4, 5}

Which of the following sets is an example of an infinite set?

<p>The set of all integers greater than 1. (B)</p> Signup and view all the answers

If x ∈ A means 'x is an element of A,' and set A = {1, 3, 5, 7, 9}, which of the following statements is true?

<p>5 ∈ A (B)</p> Signup and view all the answers

Which of the following pairs of sets, A and B, are equal?

<p>A = {a, b, c}, B = {b, a, c} (D)</p> Signup and view all the answers

Given the universal set U = {1, 2, 3, ..., 10}, which of the following sets is a subset of U?

<p>A = {1, 3, 5, 7, 9} (B)</p> Signup and view all the answers

If set A is a proper subset of set B, which of the following statements must be true?

<p>A contains some, but not all, of the elements of B. (D)</p> Signup and view all the answers

Which of the following sets is equivalent to {x | x is an even number between 1 and 9}?

<p>{2, 4, 6, 8} (C)</p> Signup and view all the answers

Given A = {1, 2, 3} and B = {2, 3, 4}, which of the following statements is true?

<p>None of the above (D)</p> Signup and view all the answers

If U is the universal set of all integers, which of the following sets is NOT a subset of U?

<p>A = {x | $x = \sqrt{2}$} (B)</p> Signup and view all the answers

Which of the following statements accurately describes a proper subset?

<p>A proper subset is a subset that is not equal to the original set. (B)</p> Signup and view all the answers

Consider A = {a, b, c}. Which of the following sets would make A a proper subset?

<p>{a, b, c, d} (B)</p> Signup and view all the answers

Given set X = {apple, banana, cherry}, which of the following sets is a proper subset of X?

<p>{apple, banana} (D)</p> Signup and view all the answers

How does set theory establish a foundation for data structures represented in computer science?

<p>By defining relationships and operations between data collections. (D)</p> Signup and view all the answers

Set A = {2, 4, 6, 8}. How many subsets does set A have?

<p>16 (A)</p> Signup and view all the answers

If set Y = {red, green, blue}, how many proper subsets does Y have?

<p>7 (B)</p> Signup and view all the answers

Which of the following is NOT a proper subset of {1, 2, 3}?

<p>{1, 2, 3} (D)</p> Signup and view all the answers

Given A = {x, y, z}, what is the number of proper subsets of A?

<p>7 (A)</p> Signup and view all the answers

Consider the universal set U = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10} and set A = {2, 4, 6, 8}. Which visual representation best describes the relationship between U and A?

<p>A Venn diagram with a rectangle labeled U, and a circle completely inside the rectangle labeled A. (D)</p> Signup and view all the answers

A set C has 5 elements. How many more subsets does C have compared to its number of proper subsets?

<p>1 (C)</p> Signup and view all the answers

Given set A = {a, b, c, d, e} and set B = {c, e, f, g}, what is the result of A - B?

<p>{a, b, d} (A)</p> Signup and view all the answers

If set X = {2, 4, 6, 8} and set Y = {1, 2, 3, 4, 5}, what is the symmetric difference of X and Y (X ⊕ Y)?

<p>{1, 3, 5, 6, 8} (D)</p> Signup and view all the answers

In a survey, it's found that out of 100 people, 60 like apples, 50 like bananas, and 20 like both. How many people like only apples?

<p>40 (A)</p> Signup and view all the answers

Suppose A = {1, 2, 3}, B = {2, 4}, and C = {3, 4, 5}. What is A ⊕ (B ∪ C)?

<p>{1, 4, 5} (D)</p> Signup and view all the answers

A school club has 30 members. 15 are in the math club, 12 are in the science club, and 5 are in both. How many students are in neither the math nor the science club?

<p>8 (C)</p> Signup and view all the answers

Consider three sets: A = {1, 2, 3, 4}, B = {3, 4, 5, 6}, and C = {4, 6, 7, 8}. What elements are in (A ∩ B) ⊕ C?

<p>{6, 7, 8} (C)</p> Signup and view all the answers

In a group of 50 people, 30 own a car, 25 own a bike, and 10 own neither. How many people own both a car and a bike?

<p>15 (B)</p> Signup and view all the answers

Given U = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10}, A = {1, 3, 5, 7, 9}, and B = {2, 4, 6, 8, 10}. Determine $(A \cup B)'$.

<p>{} (C)</p> Signup and view all the answers

Given the universal set $U = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10}$ and set $A = {2, 4, 6, 8, 10}$, what is the complement of set A, denoted as A'?

<p>$A' = {1, 3, 5, 7, 9}$ (D)</p> Signup and view all the answers

If $X = {a, b, c, d, e}$ and $Y = {c, d, e, f, g}$, which of the following represents the intersection of sets X and Y (X ∩ Y)?

<p>$X ∩ Y = {c, d, e}$ (D)</p> Signup and view all the answers

Let $P = {1, 3, 5}$ and $Q = {2, 4, 6}$. What is the union of sets P and Q (P ∪ Q)?

<p>$P ∪ Q = {1, 2, 3, 4, 5, 6}$ (C)</p> Signup and view all the answers

Given $E = {2, 4, 6, 8}$ and $F = {4, 8, 12, 16}$, what is the set difference E - F?

<p>$E - F = {2, 6}$ (D)</p> Signup and view all the answers

Consider the universal set $U = {1, 2, 3, 4, 5, 6, 7, 8}$, $A = {1, 2, 3, 4}$, and $B = {3, 4, 5, 6}$. What is $(A ∪ B)'$?

<p>$(A ∪ B)' = {7, 8}$ (D)</p> Signup and view all the answers

If the universal set $U$ is all positive integers, $A$ is the set of even numbers, and $B$ is the set of multiples of 3, what does $A ∩ B$ represent?

<p>The set of all numbers that are both even and multiples of 3. (A)</p> Signup and view all the answers

Let $U = {a, b, c, d, e, f}$, $X = {a, c, e}$, and $Y = {b, c, f}$. Determine the result of $(X - Y) ∪ (Y - X)$.

<p>$(X - Y) ∪ (Y - X) = {a, b, e, f}$ (D)</p> Signup and view all the answers

Suppose $U$ is the set of all students in a university, $A$ is the set of students taking mathematics, and $B$ is the set of students taking computer science. What does $A - B$ represent?

<p>The set of all students taking mathematics but not computer science. (B)</p> Signup and view all the answers

Flashcards

What is a Set?

A well-defined, unordered collection of objects (elements/members).

Roster Method

Listing all elements (e.g., S = {0, 1, 2, 3}).

Set Builder Method

Describing the set's contents (e.g., S = {whole numbers less than 10}).

Universal Set

Contains all relevant elements for a problem.

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Finite Set

Number of elements is countable (e.g., A = {1, 2, 3} has 3 elements).

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Equal Sets

Sets containing the exact same elements, regardless of order.

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Subset

A set fully contained within another set (or equal to it).

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Subset Symbolism

A ⊆ U if for every x: if x is an element of A then x is an element of U.

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A = {4, 5, 6} is a subset of set U

Set within a universal set

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A = {..., -8, -4, 0, 4, 8,...} is a subset of set U

The elements of set A (multiples of 4) are also elements in Set U

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Proper Subset

It is a subset that is not equal to the set it belongs to.

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A = {x | x is a rational number} is a subset of set U

A set whose elements are all rational numbers.

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A = {3a, 2x, -1y} is not a subset of set U

Symbols in set A are not necessarily elements of set U

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Set Difference (A - B)

Elements in the first set that are not in the second set.

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Symmetric Difference (A ⊕ B)

Elements in either set, but not in their intersection.

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Venn Diagram

A visual representation of sets and their relationships.

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Intersection (A ∩ B)

The region where two or more sets overlap in a Venn diagram.

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Universal Set (U)

A set containing all elements being considered.

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Null Set/Empty Set

A set containing no elements.

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Intersection of Multiple Sets

Finding common elements among multiple sets.

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Union of Sets

All elements in at least one of the sets.

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Proper Subset Definition

A ⊂ B if A ⊆ B and A ≠ B. A is a subset of B, but not equal to B.

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Number of Subsets

The number of subsets of a set with n elements is 2^n.

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Number of Proper Subsets

The number of proper subsets of a set with n elements is 2^n – 1.

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A ⊆ B

This means A is a subset of B

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A≠B

Indicates that set A is not equal to set B; they do not contain exactly the same elements.

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Set Complement (S’ or Sc)

The set of all elements in the universal set (U) that are NOT in set S.

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Set Intersection (∩)

The set containing elements that are common to both set A and set B.

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Set Union (∪)

The set containing all elements that are in set A OR in set B (or both).

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Algebra of Sets

The fundamental rules governing set operations like union, intersection, and complement.

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Set Theory

The study of sets, their properties, relationships and manipulation of sets.

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Study Notes

  • A set is a well-defined and unordered collection of objects, referred to as elements or members.
  • Sets are denoted by uppercase letters.

Determining if a Set is Well-Defined

  • A set is well-defined if its contents can be clearly and unambiguously determined.
  • The set of all official James Bond films made by EON Productions is well-defined.
  • The set of the best TV shows of all time is not well-defined.
  • The set of the top 10 selling recording artists of 2016 is well-defined.
  • The set of great rap artists is not well-defined.

Set Notation Methods

  • Roster Method: Lists all elements, e.g., S = {0, 1, 2, 3, 4, 5, 6, 7, 8, 9}.
  • Descriptive Method: Describes the set, e.g., S = {whole numbers less than 10}.

Universal Set

  • Includes of all elements relevant to a particular discussion or problem.
  • Example: U = {0, 1, 2, 3, 4, 5, 6, 7, 8, 9}, which can be divided into EVEN and ODD subsets.

Element Notation

  • x ∈ S denotes that x is an element of set S.
  • x ∉ S denotes that x is not an element of set S.

Finite vs. Infinite Sets

  • Finite Set: Contains a countable number of elements.
  • A = {whole numbers less than 5} = {0, 1, 2, 3, 4} has 5 elements.
  • B = {letters of the alphabet} has 26 elements
  • Infinite Set: Contains a non-countable number of elements.
  • X = {even whole numbers} = {2, 4, 6, 8, ...}
  • Y = {multiples of 100} = {100, 200, 300, ...}
  • The three dots (...) indicate the list continues infinitely.

Set Equality

  • Two sets are identical if and only if they contain exactly the same elements.
  • A = {9, 2, 7, -3} and B = {7, 9, -3, 2} are equal.

Subset

  • A set contained within a larger or equal set.
  • If U is the universal set of all numbers, then A is a subset of U if every element in A is also in U.
  • Symbolically, A ⊆ U if ∀x [x ∈ A → x ∈ U].

Proper Subset

  • A subset that is not equal to the set it belongs to.
  • Symbolically, A ⊂ B if A ⊆ B and A ≠ B.

Number of Subsets

  • The number of subsets of a set with n elements is 2n.
  • A = {dog, cat} has 22 = 4 subsets.
  • B = {dog, cat, bird, fish} has 24 = 16 subsets.

Number of Proper Subsets

  • The number of proper subsets of a set with n elements is 2n - 1.
  • A = {dog, cat} has 22 - 1 = 3 proper subsets.
  • B = {dog, cat, bird, fish} has 24 - 1 = 15 proper subsets.

Venn Diagrams

  • Visually represent sets and their relationships.
  • The universal set (U) is typically drawn as a large rectangle.
  • Other sets are represented by circles within this rectangle.

Set Complement

  • The complement of a set S includes all elements of the universal set U that are not in S, denoted as S' or Sc.
  • If U = {letters of the alphabet} and V = {vowels}, then V' = {not vowels or consonants}.

Set Intersection

  • The intersection of two sets A and B (A ∩ B) includes all elements belonging to both A and B.
  • If A = {girls} and B = {adults}, then A ∩ B = {adults who are girls}.
  • If C = {0, 1, 2, 3,..., 98, 99, 100} and D = {50, 100, 150, 200, 250,...}, then C ∩ D = {50, 100}.

Set Union

  • The union of two sets A and B (A ∪ B) includes all elements belonging to either A or B.
  • If A = {even numbers} and B = {odd numbers}, then A ∪ B = {even and odd numbers}.
  • If C = {1, 2, 3, 4, 5} and D = {6, 7, 8, 9, 10}, then C ∪ D = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10}.

Set Difference

  • The difference between set A and set B (A - B) is composed of elements of set A that are not in set B.
  • If A = {1, 2, 3,..., 9, 10} and B = {2, 4, 6, 8, 10}, then A - B = {1, 3, 5, 7, 9}.
  • B - A = {} (null set), all elements of set B are in set A

Symmetric Difference

  • The symmetric difference between two sets is the set of all elements present in either of the sets but not in their intersection.
  • If A = {3, 6, 9} and B = {2, 4, 6, 8, 10}, then A ⊕ B = {2, 3, 4, 8, 9, 10}.
  • The element {6} is in both sets A and B, and thus not in their symmetric difference.
  • A ∩ B = {6}, so (A ∩ B)' = A ⊕ B = {2, 3, 4, 8, 9, 10}.

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Explore set theory concepts. This includes definitions of sets, universal sets, subsets, and equivalent sets. Practice identifying well-defined, infinite, and equal sets through examples.

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