Welcome to MindCipher, a social repository of the world's greatest brain teasers, logic puzzles and mental challenges.
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
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
2 479 The Bookworm
Looking onto a shelf you see three books each labeled Volume 1, Volume 2, and Volume 3 respectively. Each book is 2.5 inches thick; that is the pages are 2 inches, and each cover .25 inches. A bo ...
Submitted by Aakash
Doable
5.3
5 15 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
10 3 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
7.8
1 3 Greatest Area
A farmer challenges an engineer, a physicist, and a mathematician to fence off the largest amount of area using the least amount of fence. The engineer made his fence in a circle and said it was th ...
Submitted by Valentin
Doable
5.0
12 2 Simple 24
Why is that if p is a prime number bigger than 3, then p^2-1 is always divisible by 24 with no remainder?
Submitted by Aakash
Doable
6.6
4 3 The Price Is Right
Many shops have prices set just under a round figure, e.g. $9.99 instead of $10.00 or $99.95 instead of $100.00 . It is assumed that this is done because the price seems lower to the consumer. But th ...
Submitted by Aakash
Hard
7.0
1 8 Right or Left?
This is interesting. Look at the animation below. Do you see the girl spinning clockwise or counter-clockwise
Easy
3.0
7 10 Cooking Time
A cook must put a souffle exactly 9 minutes at the oven, but he only have a 7 minutes hourglass and a 4 minutes hourglass. How can he measure 9 minutes with those clocks?
logic Submitted by Ravi
Doable
5.7
1 3 Classic Knights & Knaves
Raymond Smullyan has made a career of writing logic problems. His most famous have to do with a mythical island of Knights and Knaves. Knights always tell the truth, and Knaves always lie. As you a ...
Submitted by Ravi
Doable
5.5
28 45 12 Identical Balls
You have 12 identical balls. One of them is slightly different in weight than the rest. You have three weighs of a balance scale to determine which ball is different and whether it is heavier or li ...
logic brain teaser Submitted by Valentin
Doable
6.2
4 3 Up and Down
Explain the following scenario: A man lives on the twelfth floor of an apartment building. Every morning he takes the elevator down to the lobby and leaves the building. In the evening, he gets int ...
Submitted by Valentin
Hard
7.3
2 3 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
2 3 Lockers
A high school has a strange principal. On the first day, he has his students perform an odd opening day ceremony: There are one thousand lockers and one thousand students in the school. The princip ...
Submitted by Aakash
Hard
7.1