Logical Deduction Problems Flashcards

All doctors are scientists. Some scientists are artists. Which conclusion must be true?

Answer: Some scientists are doctors

Since all doctors are scientists, at least some scientists must be doctors.

If it is not raining, Maria goes jogging. Maria did not go jogging today. What can you conclude?

Answer: It is raining today

By contrapositive, if Maria did not jog, then it must be raining.

Five students — A, B, C, D, E — sit in a row. A is to the left of B. C is to the right of D. B is to the left of D. Who can be in the middle (3rd position)?

Answer: D

The order A-B-D is forced, and C is to D's right, so a valid arrangement is A-B-D-C with E anywhere, placing D third.

No reptiles are warm-blooded. All snakes are reptiles. Which statement is definitely true?

Answer: No snakes are warm-blooded

Since snakes are reptiles and no reptiles are warm-blooded, no snakes can be warm-blooded.

A store offers a discount only if a customer spends more than $100 OR uses a coupon. Tom received a discount but did not use a coupon. What must be true?

Answer: Tom spent more than $100

Since the coupon condition was not met, the other condition (spending over $100) must have been satisfied.

All members of Club X play chess. No chess players ride motorcycles. James rides a motorcycle. Which conclusion follows?

Answer: James is not a member of Club X

James rides a motorcycle, so he cannot play chess, and therefore cannot be a Club X member.

In a logic puzzle: P implies Q. Q implies R. R is false. What can you conclude about P?

Answer: P is false

By contrapositive, not-R implies not-Q, and not-Q implies not-P, so P must be false.