Puzzles 73 - Puzzle Prime

Cork in a Glass

Section: Brain Teasers Category: Science

Difficulty: Hard

You have a jar filled with water and a glass. If you pour some water into the glass and place a cork in it, the cork will float towards the edges of the glass. What is the easiest way to make the cork float towards the center?

SOLUTION

Since the liquid molecules adhere to the glass molecules on the sides of the glass, the water level there is higher and buoyancy makes the cork float in that direction. If you fill the glass all the way to the edge, then the water surface will be convex and the cork will float towards the center.

Unknown Author August 7, 2017

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Puzzle Sum 8

Section: Casual Puzzles Category: Rebus

Difficulty: Easy

What animal does this sum spell?

SOLUTION

HORNET – NET + SEAL + ARM + CLOCK – ALARM CLOCK = HORSE

Sam Loyd August 4, 2017

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Lucky Day

Section: Brain Teasers Category: Insight

Difficulty: Easy

Scientists have discovered that on one particular date in the year, there is a significantly smaller number of people who die. Do you know which one?

SOLUTION

February 29 – it happens only once every four years.

Unknown Author August 1, 2017

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Picture from Russia

Section: Brain Teasers Category: Detective

Difficulty: Advanced

Look at the picture below and answer the following questions:

What time of the day is it?
Is it early spring or a late fall?
Is the river navigable?
Which direction does the river flow? (North, East, South or West?)
Is the river deep or shallow at the side where the boat is?
Is there a bridge across the river nearby?
How far is the railroad from here?
Do the birds fly North or South?

SOLUTION

2. People are sowing the crops, so it is early spring.
8. Since it is spring, birds are flying North.
1. Since birds are flying North, the shadows are pointing East, and therefore it is morning.
4. Judging by the water around the buoy, the river is flowing South.
3. Since there is a buoy, the river must be navigable.
5. The fishing line is long, so the river must be deep.
6. There would not be a ferry if there was a bridge nearby.
7. The guy on the left looks like a railroad worker, so probably the railroad is nearby.

Unknown Author July 28, 2017

4 Comments

Gollum’s Riddle

Section: Casual Puzzles Category: Riddle

Difficulty: Medium

This thing all things devours,
Birds, beasts, trees, flowers,
Gnaws iron, bites steel,
Grinds hard stones to meal,
Slays king, ruins town,
And beats mountain down.

SOLUTION

The answer is TIME.

J. R. R. Tolkien July 25, 2017

2 Comments

Puzzle Sum 7

Section: Casual Puzzles Category: Rebus

Difficulty: Easy

What birds do these sums spell?

SOLUTION

WRENCH + ARM – CHARM = WREN
MAGNET – NET + PIE = MAGPIE

Sam Loyd July 22, 2017

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Knocked Off Piece

Section: Brain Teasers Category: Chess

Difficulty: Expert

The following position occurs in a real game, right after one of the pieces gets knocked off the board. What was the piece?

SOLUTION

It was a black knight. First, notice that the black pawns have moved 14 times diagonally and thus they have taken 14 pieces. Therefore the knocked off piece is black. Since it is impossible for both kings to be checked at the same time, the missing piece was positioned on a2. It couldn’t be a queen or a rook, because the white king would be checked both by it and the pawn on b3, which is impossible. Therefore the missing piece is either the black white-squared bishop or the black knight. However, the pawns on b7 and d7 haven’t been moved the entire game and then the black white-squared bishop hasn’t either. Thus we conclude that the knocked off piece is a black knight.

Unknown Author July 19, 2017

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Tetris Puzzle

Section: Brain Teasers Category: Mathematics

Difficulty: Advanced

As a birthday present last year, I received some fridge magnets. They didn’t come as a puzzle, so I don’t know if they have a solution, but I made a puzzle out of them anyway. The magnets are tetrominoes. There are 7 of each shape. Is it possible to arrange them into a 7×28 rectangle so that they are all used and all inside the rectangle? The closest I have managed is this:

SOLUTION

No, it is impossible. Imagine you are placing the tetrominoes on a 7×28 chess board. All of them, except for the T-shaped ones cover exactly 2 black and 2 white cells. Each of the T-shaped tetrominos covers either 2 more black cells than white cells or 2 more white cells than black cells. Since there are 7 of them, combined they will cover either more black cells than white cells or more white cells than black cells. Therefore all pieces on the picture can not cover perfectly a rectangle, which contains an equal number of black and white cells.

Source:

Puzzling StackExchange

James Webster July 16, 2017

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Out of Place

Section: Brain Teasers Category: Insight

Difficulty: Medium

Which of the numbers below is out of place and why?

1011, 2223, 3940, 5646, 8910

SOLUTION

Every number except 5646 can be split into a sequence of consecutive numbers: 1011~10-11, 2223~22-23, 3940~39-40, 8910~8-9-10.

Puzzle Prime July 13, 2017

2 Comments

Two Games at Once

Section: Brain Teasers Category: Insight

Difficulty: Medium

The Devil offers you a deal – you have to play two games of chess simultaneously against the two best GrandMasters in the world, one with black pieces and one with white pieces. If you win at least 1 point from the two games, you will get whatever your heart desires, if you don’t – you will go straight to Hell. Would you accept the challenge?

SOLUTION

Accept the challenge. You can easily get 1 point by just repeating the moves of your opponents. For example, if the white GrandMaster plays e4, then you play e4 against the black GrandMaster. If the back GrandMaster plays e5, then you play e5 against the white GrandMaster and so on.

Unknown Author July 7, 2017

2 Comments