Category: Deduction

Creepy Beasts Inc.

Category: Deduction
Difficulty:

At Creepy Beasts Inc., three of the most dreaded animals, a tiger, a wolf, and a bear, sat in their boardroom in silence while they awaited their boss. Then, Mr. Tiger broke the silence.

“Isn’t it odd that our surnames match our species, yet none of our surnames match our own?”

The wolf replied, “Yeah, but does anyone care?”

They sat in silence again…

Can you figure out the surname of each animal?

Since the wolf replied to Mr. Tiger, his surname can be neither Tiger nor Wolf. Therefore, the wolf’s surname is Mr. Bear. Subsequently, Mr. Tiger must be a bear, and finally, Mr. Wolf must be a tiger.

Unknown Author January 10, 2020
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Ten Lanterns

Category: Deduction
Difficulty:

You have ten lanterns, five of which are working, and five of which are broken. You are allowed to choose any two lanterns and make a test which tells you whether there is a broken lantern among them or not. How many tests do you need until you find a working lantern?

Remark: If the test detects that there are broken lanterns, it does not tell you which ones and how many (one or two) they are.

You need 6 tests:

(1, 2) → (3, 4) → (5, 6) → (7, 8) → (7, 9) → (8, 9)

If at least one of these tests is positive, then you have found two working lanterns.

It all of these tests are negative, then lantern #10 must be working. Indeed, since at least one lantern in each of the pairs (1, 2), (3, 4), (5, 6) is not working. Therefore, there are at least 2 working lanterns among #7, #8, #9, #10. If #10 is not working, then at least one of the pairs (7, 8), (7, 9), or (8, 9) must yield a positive test, which is a contradiction.

With some case analysis, it is not hard to see that 5 tests are not enough.

Unknown Author December 28, 2019
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Eight Queens Puzzle

Category: Deduction
Difficulty:

Rearrange the eight queens so that no two of them attack each other. For an extra challenge, make sure that no three of them lie on a straight line.

The original puzzle has 10 unique solutions, up to rotation and symmetry. With the additional restriction imposed, there is only one solution.

Max Bezzel November 28, 2019
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Three Cards

Category: Deduction
Difficulty:

There are three playing cards in a row. There is a two to the right of a king. There is a diamond to the left of a spade. There is an ace to the left of a heart. There is a heart to the left of a spade. Identify the three cards.

The cards are an Ace of Diamonds, a King of Hearts, and a Two of Spades.

Unknown Author October 28, 2019
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