Welcome to MindCipher, a social repository of the world's greatest brain teasers, logic puzzles and mental challenges.
4 4 Time To Fuse
You have a string-like fuse that burns in exactly one minute. The fuse is inhomogeneous, and it may burn slowly at first, then quickly, then slowly, and so on. You have a match, and no watch. How do ...
physics logic rates Submitted by Valentin
Doable
4.5
2 3 Nice to meet you
At a secret meeting, everyone shakes hands exactly once with every other person present. Altogether there are forty-five handshakes. How many people attended the meeting?
Easy
2.9
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
7 4 Tea and Wine
You take a spoon of wine from a barrel of wine and put it into your cup of tea. Then you return a spoon of the (non-uniform) mixture of tea and wine from your cup and put it in the barrel. Now you ha ...
Math logic Submitted by Ravi
Doable
4.7
6 2 Salary
Three coworkers would like to know their average salary. how can they do it, without disclosing their own salaries.
Submitted by Aakash
Doable
6.0
5 3 Clock Hands - Google Interview Question
How many degrees are there in the angle between the hour and minute hands of a clock when the time is a quarter past three?
logic mathematics Submitted by Valentin
Doable
3.5
4 5 Attic Light Switch
A downstairs panel contains three on-off switches. One of them controls the lamp in your attic. Using only ONE trip up to the attic, how do you determine which switch controls the lamp?
Doable
4.7
4 3 The Middle of Nowhere
What is in the middle of "nowhere"? The answer is indisputable, and not based on some philosophy.
riddle Submitted by Aakash
Easy
2.4
6 10 Find the Missing Number
In this table, each row across follows the same pattern of numbers. See if you can discern the pattern and fill in the missing number in the bottom row. 7 4 8 3 9 7 6 5 10 ? ...
patterns Submitted by Ravi
Doable
6.0
3 6 Are the lines parallel?
Are the horizontal lines in the picture parallel?
illusion Submitted by Valentin
Easy
2.4
4 2 Gone Camping
Camp Crona’s cook, Allison, was just about to begin preparing the picnic lunch for all the campers. She already knew she needed to fill 55 bowls of the same size and capacity with the same amount of fo ...
mathematics Submitted by Aakash
Easy
3.1
8 3 The Tallest Mountain
A man approaches you with a very enigmatic look on his face. He asks your for a bit of your time and if you could answer a quick question for him. He asks: “Before Mt. Everest was discovered, which w ...
riddle Submitted by Ravi
Easy
2.2
3 9 The Cabin
There is a man lying face-down, dead, in the middle of a cabin. The cabin is in the middle of the woods. There are windows, but they do not open. What is going on?
Doable
5.4
8 10 Interview Question - Databases
This is a common interview question at companies like Google and Amazon: “Explain a database in three sentences to your eight-year-old nephew.” This question has an infinite number of solutions. Fee ...
Easy
2.7
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