Logic and Lateral Thinking

Education · 20 questions

No arithmetic required, only the nerve to distrust your first answer.

Answer each question first, then check with “Show the answer”. You can also play the same quiz in the Quizera app by searching for it in Explore, as a live game, a test or flashcards.

1. All cats are mammals. No mammal is cold-blooded. What follows with certainty?

   1. Some cats are cold-blooded
   2. All mammals are cats
   3. No cat is cold-blooded
   4. Some cold-blooded animals are mammals
   Show the answer

   C) No cat is cold-blooded

2. Cards show a letter on one side, a number on the other: A, K, 4, 7. To test 'a vowel has an even number behind it', flip which two?

   1. A and 4
   2. K and 7
   3. Only A
   4. A and 7
   Show the answer

   D) A and 7

3. Behind one of three doors is a prize. You pick one; the host, who knows, opens an empty one. What is your best move?

   1. Switch to the other door
   2. Stay with your pick
   3. It makes no difference
   4. Flip a coin
   Show the answer

   A) Switch to the other door

4. A dark drawer holds 10 black and 10 navy socks. How many must you take to guarantee a matching pair?

   1. 2
   2. 3
   3. 11
   4. 20
   Show the answer

   B) 3

5. Returning warplanes were mapped for bullet holes. Where did the statistician say to add armour?

   1. Where the holes were densest
   2. Where there were no holes
   3. Evenly across the plane
   4. Only on the wingtips
   Show the answer

   B) Where there were no holes

6. 'If it rains, the match is cancelled' is true, and the match was cancelled. What follows about the rain?

   1. It definitely rained
   2. It definitely did not rain
   3. Nothing certain can be concluded
   4. There is a fifty-fifty chance
   Show the answer

   C) Nothing certain can be concluded

7. Two people played five games of chess and each won three. There were no draws. How is that possible?

   1. They were not playing each other
   2. Someone cheated
   3. One game was counted twice
   4. It is impossible
   Show the answer

   A) They were not playing each other

8. A surgeon looks at the patient and says 'This is my son, but I am not his father.' Who is the surgeon?

   1. His stepfather
   2. His uncle
   3. His godfather
   4. The boy's mother
   Show the answer

   D) The boy's mother

9. On an island where everyone always lies or always tells the truth, someone says 'I am a liar.' What follows?

   1. The speaker is a liar
   2. The speaker cannot be an islander
   3. The speaker is truthful
   4. The speaker is half truthful
   Show the answer

   B) The speaker cannot be an islander

10. A disease affects 1 in 10,000 people. A 99% accurate test comes back positive. What is the chance of illness?

    1. Still quite low
    2. About 99 percent
    3. About 50 percent
    4. Effectively certain
    Show the answer

    A) Still quite low

11. In the sequence 1, 11, 21, 1211, 111221, how is each term produced?

    1. By adding the digits
    2. By doubling the number
    3. By reading the previous term aloud
    4. By reversing the digits
    Show the answer

    C) By reading the previous term aloud

12. Three bulbs in a closed room are wired to three switches outside. You may enter once. How do you match them?

    1. Flick the switches rapidly
    2. Peer through the door crack
    3. Leave all three switches on
    4. Leave one switch on a while, then turn it off
    Show the answer

    D) Leave one switch on a while, then turn it off

13. Which of these terms includes all of the other three?

    1. Square
    2. Parallelogram
    3. Rectangle
    4. Rhombus
    Show the answer

    B) Parallelogram

14. Which is logically more probable: 'Ann is a bank teller' or 'Ann is a bank teller and an activist'?

    1. They are equally probable
    2. Bank teller and activist
    3. It cannot be determined
    4. Bank teller alone
    Show the answer

    D) Bank teller alone

15. A single counterexample is enough to disprove a universal claim.

    1. True
    2. False
    Show the answer

    A) True

16. If 'all A are B' is true, then 'all B are A' must also be true.

    1. True
    2. False
    Show the answer

    B) False

17. A valid argument guarantees that its conclusion is true in the real world.

    1. True
    2. False
    Show the answer

    B) False

18. If two things are observed together, one of them must be causing the other.

    1. True
    2. False
    Show the answer

    B) False

19. A claim being unproven does not by itself make the claim false.

    1. True
    2. False
    Show the answer

    A) True

20. A palindrome reads the same forwards and backwards.

    1. True
    2. False
    Show the answer

    A) True