Welcome to MindCipher, a social repository of the world's greatest brain teasers, logic puzzles and mental challenges.
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
2.4
7 2 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
4.0
6 8 Non-Adaptive 12 Identical Balls
Okay - so I posted this puzzle to reddit a few weeks ago and one guy had the following comment: Same problem, but your solution must be non-adaptive. IOW, specify the weighings that you will make up f ...
Math logic unsolved Submitted by Aakash
Hard
8.7
7 7 The Famous Hole in a Sphere
This incredible problem was first made famous by Martin Gardner with his ‘Mathematical Games’ column published in Scientific American throughout the 60s and 70s. A cylindrical hole, 6 inches long, ...
Math Lateral geometry Submitted by Ravi
Hard
6.7
4 2 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
2.3
6 4 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
8 2 Measuring Up
You have a 3 and a 5 litre water container, each container has no markings except for that which gives you its total volume. You also have a running tap. You must use the containers and the tap in su ...
logic brain teaser Submitted by Ravi
Doable
3.3
11 1 Choose the Next Letter
Choose the next letter in the sequence: O T T F F S S ?
logic patterns sequences Submitted by Ravi
Easy
3.1
7 6 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
2.8
5 8 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
6 6 The Neighbourhood
People say Einstein suggested that 98% of the world’s population couldn’t figure out the answer to this puzzle. It is not for the faint of heart: There are 5 houses each with a different color. Th ...
Hard
7.3
5 12 Crazy Google Interview Question
You are shrunk to the height of a nickel and your mass is proportionally reduced so as to maintain your original density. You are then thrown into an empty glass blender. The blades will start moving ...
Doable
6.0
8 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
3.8
7 3 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
4.9
9 1 Mutilated Chessboard Problem
Suppose a standard 8×8 chessboard has two diagonally opposite corners removed, leaving 62 squares. Is it possible to place 31 dominoes of size 2×1 so as to cover all of these squares?
geometry chess proofs Submitted by Ravi
Hard
7.1