Onto Functions - Discrete Structures - Solved Exam, Exams of Discrete Structures and Graph Theory

These solved exam paper are very easy to understand and very helpful to built a concept about the foundation of computers and discrete structures.The key points discuss in these notes are:Onto Functions, Tautology, Contradiction, Map Sets, Negation of Implication, Density of Binary String, Conditional Statement, Set of Rational Numbers, Laws of Logic, Universal Conditional, Rules of Inference

Typology: Exams

2012/2013

Uploaded on 04/27/2013

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Spring 2011 Examination 1 CMSC 203 Name SOLUTION KEY
1. (20 points) Circle T for True or F for False as they apply to the following statements:
T F A statement is either a tautology or a contradiction.
T F The set {a, e, i, o, u, y} has 64 subsets.
T F The empty set is a subset of itself.
T F Onto functions map sets to sets of equal or smaller size.
T F If Σ
= {0, 1} , then Σ
3
= {000, 111}.
T F The negation of an implication is an implication.
T F The density of a binary string equals its length.
T F If Σ
= {0, 1}, then for any string s in Σ
8
, H(s, 11111111) = d( s ).
T F The conditional statement and its converse are logically equivalent.
T F The set of Rational numbers is countable.
2. (10 points) Use the Laws of Logic to show:
¬
p
(q
¬
r)
¬
[ (r
q)
p ]
¬
p
(q
¬
r)
¬
p
(
¬
r
q)
¬
p
(r
q)
¬
[ p
¬
(r
q) ]
¬
[
¬
(r
q)
p ]
¬
[ (r
q)
p ]
3. (6 points) Find the negation of the following Universal Conditional:
Some people who like Math study Economics.
All people like Math and do not study Economics.
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1. (20 points) Circle T for True or F for False as they apply to the following statements:

T F A statement is either a tautology or a contradiction.

T F The set {a, e, i, o, u, y} has 64 subsets.

T F The empty set is a subset of itself.

T F Onto functions map sets to sets of equal or smaller size.

T F If Σ = {0, 1} , then Σ^3 = {000, 111}.

T F The negation of an implication is an implication.

T F The density of a binary string equals its length.

T F If Σ = {0, 1}, then for any string s in Σ^8 , H( s , 11111111) = d( s ).

T F The conditional statement and its converse are logically equivalent.

T F The set of Rational numbers is countable.

2. (10 points) Use the Laws of Logic to show: ¬ p ∧ ( q ∨ ¬ r ) ≡ ¬ [ ( r → q ) → p ]

¬ p ∧ ( q ∨ ¬ r ) ≡ ¬ p ∧ (¬ r ∨ q ) ≡ ¬ p ∧ ( r → q ) ≡ ¬ [ p ∨ ¬ ( r → q ) ]

≡ ¬ [ ¬ ( r → q ) ∨ p ]

≡ ¬ [ ( r → q ) → p ]

3. (6 points) Find the negation of the following Universal Conditional: Some people who like Math study Economics.

All people like Math and do not study Economics.

4. (10 points) Use the Rules of Inference to show the following is a valid argument:

p → q

¬ r → ¬ q

r → ( s ∧ u )

p

∴ s

1. p → q AND p THEREFORE q ;

2. ¬ r → ¬ q AND q THEREFORE r ;

3. r → ( s ∧ u ) AND r THEREFORE ( s ∧ u );

4. ( s ∧ u ) THEREFORE s.

5. (10 points) Given the alphabet Σ = {0,1}, list the subsets of Σ^4 where each subset contains the

elements of Σ^4 that have the same Hamming Distance from 1100.

s 0000 0001 0010 0011 0100 0101 0110 0111 1000 1001 1010 1011 1100 1101 1110 1111 H(1100, s ) 2 3 3 4 1 2 2 3 1 2 2 3 0 1 1 2

H(1100, s ) = 0: { 1100 } H(1100, s ) = 1: { 0100, 1000, 1101, 1110 } H(1100, s ) = 2: { 0000, 0101, 0110, 1001, 1010, 1111 } H(1100, s ) = 3: { 0001, 0010, 0111, 1011 } H(1100, s ) = 4: { 0011 }

6. (10 points) Using the Properties of Sets, to show (A − B) ∪ (A ∩ B) ∪ (B − A) = A ∪ B.

(A − B) ∪ (A ∩ B) ∪ (B − A) = (A ∩ Bc) ∪ (A ∩ B) ∪ (B ∩ Ac)

= (A ∩ Bc) ∪ (A ∩ B) ∪ (A ∩ B) ∪ (B ∩ Ac) = [ A ∩ (Bc^ ∪ B)] ∪ [(A ∪ Ac) ∩ B] = (A ∩ U) ∪ (U ∩ B) = A ∪ B.