Propositional logic & proofs worksheet with answers

Free printable Propositional logic & proofs worksheet: 6 problems from easy to exam level, with an answer key. Print it or save it as a PDF.

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1.Easy
pqr((q ∧ p) ∧ r) ∧ (q ∨ (r ∨ p))111110101100011010001000

Exactly one row of the truth table makes ((q ∧ p) ∧ r) ∧ (q ∨ (r ∨ p)) true. Click that row.

((q ∧ p) ∧ r) ∧ (q ∨ (r ∨ p))
  1. 1p = 1, q = 1, r = 1
  2. 2p = 1, q = 1, r = 0
  3. 3p = 1, q = 0, r = 1
  4. 4p = 1, q = 0, r = 0
  5. 5p = 0, q = 1, r = 1
  6. 6p = 0, q = 1, r = 0
  7. 7p = 0, q = 0, r = 1
  8. 8p = 0, q = 0, r = 0
2.Easy
pqr(q ↔ ¬p) → r111?110?101?100?011?010?001?000?

Complete the truth table (1 = true, 0 = false). In how many rows N is (q ↔ ¬p) → r true?

(q ↔ ¬p) → r
N =
3.Medium
r ∧ (p → q)(r → q) ∧ (p → q)r → (p → q)(r → p) → q

Which formula is logically equivalent to (r ∧ p) → q? Click it.

(r ∧ p) → q
  1. 1r ∧ (p → q)
  2. 2(r → q) ∧ (p → q)
  3. 3r → (p → q)
  4. 4(r → p) → q
4.Medium
abc¬((c ↔ b) ↔ a)(b → (¬c ∧ a)) → ¬((c ↔ b) ↔ a)¬((b → (¬c ∧ a)) → ¬((c ↔ b) ↔ a))111?110?101?100?011?010?001?000?

In how many of the 8 rows of its truth table is ¬((b → (¬c ∧ a)) → ¬((c ↔ b) ↔ a)) true? Call this number N.

¬((b → (¬c ∧ a)) → ¬((c ↔ b) ↔ a))
N =
5.Hard
∀x (¬A(x) ∧ ¬B(x))∃x (¬A(x) ∨ ¬B(x))∀x (¬A(x) ∨ ¬B(x))∃x (¬A(x) ∧ ¬B(x))

Which statement is equivalent to ¬∀x (A(x) ∨ B(x)), with the negation moved all the way inside? Click it.

¬∀x (A(x) ∨ B(x))
  1. 1∀x (¬A(x) ∧ ¬B(x))
  2. 2∃x (¬A(x) ∨ ¬B(x))
  3. 3∀x (¬A(x) ∨ ¬B(x))
  4. 4∃x (¬A(x) ∧ ¬B(x))
6.Hard
pqp → q¬p¬q11100100

The argument with premises p → q; ¬p and conclusion ¬q is invalid. Click the row of the truth table that is a counterexample.

p → q¬p∴ ¬q
  1. 1p = 1, q = 1
  2. 2p = 1, q = 0
  3. 3p = 0, q = 1
  4. 4p = 0, q = 0

Answer key

  1. 1. p = 1, q = 1, r = 1
  2. 2. N = 6
  3. 3. r → (p → q)
  4. 4. N = 2
  5. 5. ∃x (¬A(x) ∧ ¬B(x))
  6. 6. p = 0, q = 1

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