Out of Place
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.
Difficulty: Medium
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Two Games at Once
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.
Digital Scale
You have 10 unlimited piles of balls and one digital scale. All balls in a pile have the same weight, which is an integer between 1 and 9 grams. How many measurements do you need in order to find the weight of the balls in every pile?
SOLUTION
You need only one measurement – take 1 ball from pile 1, 10 balls from pile 2, 100 balls from pile 3, etc., and measure their total weight. The first digit of the number shown on the scale determines the weight of the balls in the 10th pile, the second digit determines the weight of the balls in the 9th pile and so on.
Wine and Water
You have two 1 liter mugs – one of them halfway filled with water and the other one halfway filled with wine. You pour 300ml water from the first mug into the second one, stir it well, then pour 300ml of the mix from the second mug back to the first one. Now
SOLUTION
If you have X ml water in the first mug, then in the second mug you have 500-X ml water and X ml wine. Therefore you have exactly as much water in the first mug as you have wine in the second one.
Hourglasses
You have a 7-minute hourglass and an 11-minute hourglass. How can you measure exactly 15 minutes with them?
SOLUTION
Turn both hourglasses upside down. When the time of the 7-minute hourglass runs out, turn it upside down. When the time of the 11-minute hourglass runs out, turn the 7-minute hourglass upside down again. Finally, when the time of the 7-minute hourglass runs out, exactly 15 minutes will have been passed.
Slowest Horse
Two friends made a bet whose horse is slower. After wondering for days what is the fastest and fairest way to figure out who wins the bet, they finally decided to ask a famous wise hermit for help. Upon giving them his advice, the two friends jumped on the horses and started racing back to the city as fast as they could. What did the hermit say?
SOLUTION
He told them to switch their horses and whoever gets to the city first will win the bet.
Illusion Maze
Find a path between the two squares in this Illusion Maze, created by Dave Phillips.
SOLUTION
The solution is shown below.
Funky Mate
Place only 2 rooks and 1 knight on the board, so that the Black player is mated.
SOLUTION
You can place the rooks on c5 and e5, and the knight on f5.
Angry Men
You must go through this maze, avoiding the 16 angry men’s batons. You are allowed to press once each of the four buttons on the walls, which make the men turn clockwise at 90 degrees.
SOLUTION
The solution is shown below.
Snail on a Tree
A snail is trying to climb a
SOLUTION
Seven days only. After the sixth day, the snail would have climbed 6 meters. During the seventh day, it will climb 4 more meters and will get to the top.