2 Matchsticks, 4 Squares
Move only 2 matchsticks so that you get 4 (identical) squares. There should not be any spare matchsticks left.
SOLUTION
The solution is shown below.
Category: Brain Teasers
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Programmers and Coins
One programmer draws on a sheet of paper several circles in a line, representing coins, and puts his thumb on the first circle, covering the rest with his hand. Then he asks another programmer to guess how many different head-tail combinations are possible if someone flips all the (imaginary) coins on the paper. The second programmer, without knowing the number of circles, takes the pen and writes down a number. Then the first programmer lifts his hand and sees that the correct answer is written on the paper. How did the second programmer manage to do this?
SOLUTION
The second programmer wrote down “1” in front of the first circle. When the second programmer lifted his hand, he saw the number “10…00”, which is exactly the number of possible head-tail combinations in binary system.
Unusual Position
What is the smallest number of moves needed to result in this unusual position?
SOLUTION
The shortest game takes just 4 moves:
1. Nf3 e5
2. Nxe5 Ne7
3. Nxd7 Nec6
4. Nxb8 Nxb8
Pass Through a Card
Take a small piece of paper – 4in by 6in, and scissors. Can you cut the paper in such a way, so that you can pass through it
SOLUTION
Yes, you can, as shown on the image below.
Be brave!
Which is the best move for White in this position?
SOLUTION
The best move is 1. Rc8+. Then either 1. … Kxb7 2. Rxd8, or 1. … Rxc8 2. Qxa7 Kxa7 3. bxc8 = N+, and Black loses both the Rook and the Queen.
Complex Timepiece
A sundial has the fewest moving parts of any timepiece. Which has the most?
SOLUTION
The hourglass, it has thousands of grains of sand.
The Pasta Puzzle
You have 10 strings of pasta left on your plate. You randomly start tying up their ends, until there are no loose ends anymore. What is the average number of loops which are created?
SOLUTION
The expected (average) number of loops at the end of the procedure is equal to the expected number of loops created after the first tying, plus the expected number of loops created after the second tying, etc. After each tying, the number of non-loop strings decreases by 1, and then the probabilities to create a new loop are 1/19, 1/17, 1/15, etc. Therefore, the answer is the sum 1/19 + 1/17 + 1/15 + … + 1/3 + 1/1 ~ 2.1.
Versatile Word
What four-letter word can be written forward, backward or upside down, and can still be read from left to right?
SOLUTION
The word NOON.
Brick Measurement
Imagine you have three identical bricks and want to find the common length of their main diagonals. What is the easiest way to do this using just a measuring tape?
SOLUTION
PLace the bricks as shown on the image below, then measure the marked segment.
Slicing a Bagel
Get a bagel and a knife, then cut the bagel in two pieces which end up linked to each other.
SOLUTION
The solution is presented HERE.
