Welcome to MindCipher, a social repository of the world's greatest brain teasers, logic puzzles and mental challenges.
5 1 3 Brilliant People
There are three genii standing in a row in a room facing the same direction. Thus, the genius at one end can see the two genii ahead of him, the genius in the middle can only see the one genius ahea ...
Submitted by Ravi
Doable
4.3
4 2 The Classic Weights & Scale
You have 8 lead marbles, one of which is heavier than the rest. What is the minimum amount of “weightings” (i.e. with a see-saw scale) you need to do to guarantee finding the odd one out?
Submitted by Valentin
Doable
4.3
3 1 What number is next?
What number comes next in this sequence? 4, 20, 56, 120, 220, ?
Submitted by Aakash
Doable
4.3
7 5 Burning Rope
There are two lengths of rope. Each one can burn in exactly one hour. They are not necessarily of the same length or width as each other. They also are not of uniform width (may be wider in middle th ...
Submitted by Ravi
Doable
4.3
6 6 The Female Star
My first two letters are a man. The first three a woman. The first four are a brave man. And in whole I am a brave woman.
riddle word puzzle Submitted by Valentin
Doable
4.3
18 4 3 Men and a Hotel Room
Three men decided to split the cost of a hotel room. The hotel manager gave them a price of $30. The men split the bill evenly, each paying $10, and retired to their room. However, the manager real ...
Submitted by Valentin
Doable
4.2
8 2 All Apples
On the market, mrs. Jones and mrs. Smith sell apples. Mrs. Jones sells her apples per two for 0.50 euro. The apples of Mrs. Smith are a bit smaller; she sells hers per three for 0.50 euro. At a certa ...
mathematics ratios Submitted by Valentin
Doable
4.0
4 7 Balloon Business
You’re sitting in a stationary car. There’s a helium balloon tied to its floor. You accelerate and, obviously feel like you’re being pushed backwards (against the direction of your acceleration). W ...
physics science logic Submitted by Valentin
Doable
4.0
0 4 Plane In The Wind
An airplane flies in a straight line from airport A to airport B and back. It has constant engine speed and no wind. Will its total flight time increase, decrease or stay the same if throughout bot ...
Submitted by Valentin
Doable
4.0
3 4 Products Algorithm
Given an array A[1...N] of integers, create an array O[1...N] where O[i] = the product of all elements in A except for the ith element. For example, if N = 3, and A = {6, 4, 2}, O = {8, 12, 24} The t ...
Doable
4.0
2 2 The Number Problem
What does 3685=? 8809=6 7111=0 2172=0 6666=4 1111=0 3213=0 7662=2 8096=5 9312=1 4444=0 6824=3 9999=4 0345=1 2359=1 5522=0 9884=5 Enjoy, this is quite interesting.
Submitted by Ravi
Doable
4.0
15 14 Swap Variables in Place without XOR
Suppose you have two variables, a and b. How can you swap their values without using a temporary variable and also without using the bitwise operator XOR?
Doable
3.9
12 3 Choose the Next Letter
Choose the next letter in the sequence: O T T F F S S ?
logic patterns sequences Submitted by Ravi
Doable
3.8
7 8 Bug's Eye
You are a bug sitting in one corner of a cubic room. You wish to walk (not fly) to the extreme opposite corner – the corner furthest from you. Describe the shortest path that you can walk.
geometry trigonometry Submitted by Ravi
Doable
3.8
4 5 Electrical Deaths
You and your friend are driving out in the pouring rain one night. It soon becomes much to hard too see, so you stop at closest house possible. When you knock on the door, an old lady welcomes you to ...
brain teaser riddle Submitted by Ravi
Doable
3.7