Welcome to MindCipher, a social repository of the world's greatest brain teasers, logic puzzles and mental challenges.
1 1 Stuck in a brick building
A man is stuck inside an all brick building (floor, ceiling, and walls are all brick), that has no windows and no doors, and inside with him he has only a wooden board and a saw, how does he get out? ...
Submitted by Valentin
Doable
5.3
3 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
5.2
4 Cards With Crosses
You have a stack of 23 cards. Each card has an image of a cross on one side, and an image of a circle on the other side. You know that 14 cards in the stack are laying with the cross up, and therefor ...
Submitted by Valentin
Doable
6.0
3 What am I?
The first person makes me and sells me. The second person buys me but doesnt use me. The third person uses me but doesnt see me. What am I?
Submitted by Valentin
Hard
6.8
3 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
Easy
3.0
2 Farmer's Market
You’re a farmer. You’re going to a market to buy some animals. On the market there are 3 types of animals for sale. You can buy: Horses for £10 each, goats for £1 each and ducks, you get 8 of these ...
Submitted by Aakash
Doable
5.2
3 1 Its waistline is a hexagon
Heart of Darkness, Coat of Grain, Was once alive, Now feels no pain, Never walks, but Leaves a Trail. Circle head and pointed tail. Grows shorter as the day goes on- Its waistline is a hexagon. Wha ...
Submitted by Valentin
Doable
3.3
3 What number is next?
What number comes next in this sequence? 4, 20, 56, 120, 220, ?
Submitted by Aakash
Doable
5.0
3 Power of 2 (Microsoft Interview)
Given any number n, using one line of C (using no external libraries or functions) code, determine if n is a power of 2. Return 1 if n is a power of 2 and 0 if not.
bitwise powers Submitted by Aakash
Doable
6.0
1 2 The Way Engineers Think
A priest, a doctor, and an engineer were waiting one morning for a particularly slow group of golfers. Engineer: What’s with these guys? We must have been waiting for 15 minutes! Doctor: I don’t ...
Submitted by Aakash
Doable
6.0
1 3 Right or Left?
This is interesting. Look at the animation below. Do you see the girl spinning clockwise or counter-clockwise
Doable
3.3
3 The fake coin
You have 9 coins which all look identical but 1 of them weight less than the others. You have a two pan balance (see the picture) with which you can measure twice, and with this 2 measurements you ha ...
Submitted by Aakash
Doable
4.0
1 2 Marble Weights
You are given a set of scales and 12 marbles. The scales are of the old balance variety. That is, a small dish hangs from each end of a rod that is balanced in the middle. The device enables you to c ...
Submitted by Ravi
Doable
6.0
0 The fisherman and the Hunter
The are two men that always tell the truth except for the days when they are lying. The fisherman lies on Monday, Tuesday and Wednesday. The Hunter lies on Thursday, Friday and Saturday. Today the ...
Submitted by Valentin
Easy
2.8
1 2 Running Race
Phil and Sal race each other for 100 yards. Sal wins by 10 yards. They decide to race again, but this time, to even things up, Sal begins 10 yards behind the start line. Assuming that both run with t ...
Submitted by Aakash
Doable
4.0