Welcome to MindCipher, a social repository of the world's greatest brain teasers, logic puzzles and mental challenges.
12 1 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
6 9 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
5 2 Matchsticks
This is a classic Martin Gardner puzzle. See the picture - the four matchsticks represent a martini glass and the match head represents an olive. Move just two matches so that the glass is reformed bu ...
logic spatial Submitted by Aakash
5 6 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
5 5 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?
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
4 3 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
2 12 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
9 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?
4 3 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?
7 1 The bus stop
You’re driving your car to work in the pouring rain when you see three people on the side of the road at an uncovered bus stop. You recognize one as your best friend waiting to go to work, the second ...
Submitted by Aakash
4 2 No if() no abs()!
This is inspired by the puzzle "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 +- · / (basic arithmetic operator ...
5 4 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
4 1 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
4 1 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