Welcome to MindCipher, a social repository of the world's greatest brain teasers, logic puzzles and mental challenges.
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
8 1 Attic Lamp 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?
logic brain teaser Submitted by Valentin
Doable
5.3
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
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
9 11 The Monty Hall Problem
You’re on a game show, and you’re given the choice of three doors: Behind one door is a car and behind the other two doors are goats. You pick a door, say No. 1, and the host, who knows what’s behind ...
Doable
5.5
12 7 Carpeting a Donut
Given two concentric circles and a chord of the outer circle, tangent to the inner circle, of length 25m, find the area between the two circles. See illustration. No other information needed, all you n ...
Doable
5.5
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
37 27 No if() Only abs()
Given two variable a and b, construct a function f(a,b) which return the maximum one in {a,b}. You can only use +- · / and abs() (to take the absolute value). NO if() is allowed in your construction. ...
Submitted by MoralMachine
Doable
5.8
10 211 Fork in the road
You are walking down a road and arrive at a fork that splits the road into two separate paths. When you reach, you meet two identical twins, each standing at the edge of one of the two paths. You h ...
Submitted by Aakash
Doable
6.0
14 82 Coin Flip
On Monday, you flip a coin all day. You start flipping it until you see the pattern Head, Tail, Head. You record the number of flips required to reach this pattern, and start flipping again (and co ...
Math statistics Submitted by Aakash
Doable
6.0
5 3 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
1 1 Find these Hollywood movies based on the title styles
Are you a movie buff ! Find these Hollywood movies based on the title styles !!
Doable
6.0
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
2 3 Use your mobile
In this puzzle I have given a message in a coded language. try to solve it. Message: 936382004221833200416381004381 Hint is in the title of this puzzle
Submitted by Rohan Umesh
Doable
6.0
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