Welcome to MindCipher, a social repository of the world's greatest brain teasers, logic puzzles and mental challenges.
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
5 7 Betsy and Patsy
“We were born on the same day of the same year,” said Betsy. “And we have the same mother and father,” said Patsy. “But we’re not twins!” the two exclaimed. Can you explain?
Doable
3.5
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
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
4 6 Guilty Innocence
I am a drug dealer. I have been questioned by the police with all of my drugs surrounding me, but I was not arrested. Why?
Easy
2.8
6 10 Psycho Killer
While at the funeral of her mother, she met a man whom she did not know. She thought he was amazing, her dream guy, and she fell in love with him but never asked for his number and could not find him ...
Submitted by Valentin
Easy
3.0
5 2 Age of Three Kids
One day, a guy from census come into a house. When he rings the bell, a lady comes out. He then asks how many people lives in her house, and their age. And then she says: I am 45 years old. I have thr ...
Doable
6.0
5 7 Balloon in an Elevator
A person is holding on to a helium balloon in an elevator. The elevator cable snaps, and at the exact same moment, the person lets go of the helium balloon. In the perspective of the person in the el ...
physics relativity Submitted by Aakash
Hard
7.7
6 6 The Female Star
My first two letters are a man. The first three a woman. The first four are a brave man. And in whole I am a brave woman.
riddle word puzzle Submitted by Valentin
Doable
4.3
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
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 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 13 Good luck at an interview with Google
I just came across these Google interview questions… impossible: How many golf balls can fit in a school bus? How much should you charge to wash all the windows in Seattle? How many piano tuners are ...
google open-ended Submitted by Valentin
Hard
7.0
9 1 Unfair Coin
Say you have an unfair coin: a coin whose probability of flipping heads and flipping tails is unknown but nonzero. Can you design a game where you and your opponent have an equal chance of winning?
Doable
5.0
3 6 Are the lines parallel?
Are the horizontal lines in the picture parallel?
illusion Submitted by Valentin
Easy
2.4