CCTST Deductive Reasoning 4 — Questions and Answers
Question 1: All birds have wings. Penguins are birds. Which statement must be true?
- Penguins can fly
- Penguins have wings (Correct answer)
- All winged animals are birds
- Penguins are not birds because they cannot fly
Correct answer: Penguins have wings
Universal syllogism: penguins belong to the class birds, so they inherit the property of having wings.
Question 2: If a shape has four equal sides and four right angles, it is a square. Shape Q has four equal sides but its angles are not all right angles. What follows?
- Shape Q is a square
- Shape Q is not a square (Correct answer)
- Shape Q is a rectangle
- Shape Q has no angles
Correct answer: Shape Q is not a square
Both conditions (equal sides AND right angles) are required; missing one is sufficient to conclude Shape Q is not a square.
Question 3: No valid argument has a false conclusion when its premises are true. Argument Z has true premises and a false conclusion. What follows?
- Argument Z is valid
- Argument Z is not valid (Correct answer)
- Argument Z is sound
- Argument Z has false premises
Correct answer: Argument Z is not valid
The definition directly excludes Argument Z: true premises with a false conclusion = invalid.
Question 4: All lawyers passed the bar exam. Some bar exam passers work in tech. What must be true?
- All lawyers work in tech
- Some lawyers work in tech
- No lawyers work in tech
- Nothing certain can be said about lawyers in tech (Correct answer)
Correct answer: Nothing certain can be said about lawyers in tech
The 'some' who work in tech may or may not overlap with the lawyers subset; no conclusion is forced.
Question 5: If you are a citizen, you may vote. If you may vote, you can influence elections. Carlos is a citizen. What follows?
- Carlos cannot vote
- Carlos can influence elections (Correct answer)
- Carlos is a politician
- Carlos voted in the last election
Correct answer: Carlos can influence elections
Chained modus ponens: citizen → may vote → can influence elections, and Carlos is a citizen.
Question 6: No herbivores eat meat. A wolf eats meat. What must be true about the wolf?
- The wolf is a herbivore
- The wolf is not a herbivore (Correct answer)
- The wolf sometimes eats plants
- The wolf is an omnivore
Correct answer: The wolf is not a herbivore
Because herbivores never eat meat and the wolf does, the wolf cannot be a herbivore.
Question 7: All employees must wear badges. Everyone wearing a badge has access to the building. Which conclusion is valid?
- All employees have access to the building (Correct answer)
- All people with access are employees
- Some employees lack building access
- Badges are optional for managers
Correct answer: All employees have access to the building
Employees → badges → building access; chaining gives all employees access to the building.
CCTST Deductive Reasoning 4
All birds have wings.
Penguins are birds.
Which statement must be true?