[SOLVED] CSE211 - Homework 1

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Problem 1: Conditional Statements                                                                                                        

State the converse, contrapositive, and inverse of each of these conditional statements.

  • If it snows tonight, then I will stay at home.

(Solution) Converse:

Contrapositive:

Inverse:

  • I go to the beach whenever it is a sunny summer day.

(Solution) Converse:

Contrapositive:

Inverse:

  • When I stay up late, it is necessary that I sleep until noon.

(Solution) Converse:

Contrapositive:

Inverse:

1

Problem 2: Truth Tables For Logic Operators                                                                                       (5+5+5=15 points)

Construct a truth table for each of the following compound propositions.

  • (p ⊕¬ q)

(Solution)

  • (p ⇐⇒ q) ⊕ ( ¬ p ⇐⇒ ¬ r)

(Solution)

  • (p ⊕ q) ⇒ (p ⊕¬ q)

(Solution)

Problem 3: Logic in Algorithms

(10+10+10=30 points)

If x = 1 before the statement is reached, what is the value of x after each of these statements is encountered in a computer program? Why? Show your work step by step. (a) for i ⇐ 1 to 10 do if x + 2 = 3 then x := x + 1

end

(Solution)

  • for i ⇐ 1 to 5 do if (x + 1 = 2) XOR (x + 2 = 3) then x := x + 1

end

(Solution)

  • for i ⇐ 1 to 4 do if (2x + 3 = 5) AND (3x + 4 = 7) then x := x + 1

end

(Solution)

Problem 4: Proof by contradiction

(20 points)

Show that at least three of any 25 days chosen must fall in the same month of the year using a proof by contradiction. Explain your work step by step.

(Solution)

Problem 5: Proof by contraposition

(20 points)

Show that if n3 + 5 is odd, then n is even using a proof by contraposition. Explain your work step by step. Note: Assume that n is an integer. (Solution)