Welcome to MindCipher, a social repository of the world's greatest brain teasers, logic puzzles and mental challenges.
4 5 Attic Light 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?
Doable
4.7
4 7 Balloon Business
You’re sitting in a stationary car. There’s a helium balloon tied to its floor. You accelerate and, obviously feel like you’re being pushed backwards (against the direction of your acceleration). W ...
physics science logic Submitted by Valentin
Doable
4.0
4 4 Microsoft Interview Question - Count it Out
This problem is more targeted towards people with Computer Science or similar backgrounds, it is a REAL question from an interview with Microsoft. You have an array of 99 unique numbers from 0-100. ...
Submitted by Aakash
Doable
4.9
4 3 Divide 1 to 20
What is the smallest whole number that can be divided by any number from 1 to 20 (inclusive) and not leave a remainder? For example, 60 is the smallest number that can be divided evenly by all the n ...
mathematics Submitted by Aakash
Doable
5.0
5 3 Don't Eat Me!
Would you rather a crocodile attack you or an alligator?
Submitted by Aakash
Doable
4.9
3 6 Tooth Paste, : Profit
There are 2 Persons, Who Saves Money. One person Bought a tooth Paste of 100 gms, for Rs. 40. The second person Buys, Two 50 gms for Rs. 20 each. at same shop, the same company of Pastes. No Extra past ...
Doable
6.0
2 3 Nice to meet you
At a secret meeting, everyone shakes hands exactly once with every other person present. Altogether there are forty-five handshakes. How many people attended the meeting?
Easy
2.9
4 3 Don't Hang Yourself
A fool wants to tie a rope around the earth. So he buys a rope of 40,000 KM and ties it around the world. His neighbour, also a fool, wants to do the same only he wants the rope on sticks 1 meter abo ...
Easy
3.1
1 8 Parodoxical Statements from Life
Nobody goes to that restaurant; it’s too crowded. Don’t go near the water ’til you have learned how to swim. The man who wrote such a stupid sentence can not write at all. If you get this messa ...
paradox Submitted by Ravi
Doable
5.2
3 4 Ball Drop
A man is floating in a hot air balloon off the coast of Ireland. In one hand he has a bowling ball, and in the other a golf ball, and he drops them both over the side at the same time. which one ...
Easy
3.1
5 4 Birthday Problem (Classic)
A classic problem. How many people do you need to have in a room so that the probability of at least 2 of people sharing a birthday is greater than 50%. Assume 365 days in a year (no leap years) ...
Submitted by Valentin
Hard
8.4
3 4 Products Algorithm
Given an array A[1...N] of integers, create an array O[1...N] where O[i] = the product of all elements in A except for the ith element. For example, if N = 3, and A = {6, 4, 2}, O = {8, 12, 24} The t ...
Doable
4.0
6 2 Salary
Three coworkers would like to know their average salary. how can they do it, without disclosing their own salaries.
Submitted by Aakash
Doable
6.0
4 2 The Classic Weights & Scale
You have 8 lead marbles, one of which is heavier than the rest. What is the minimum amount of “weightings” (i.e. with a see-saw scale) you need to do to guarantee finding the odd one out?
Submitted by Valentin
Doable
4.3
4 4 Left Hands Only
Assume there are approximately 6,000,000,000 (6 billion) people on Earth. What would you estimate to be the result if you multiply together the number of fingers on every person’s left-hands? For t ...
Submitted by Aakash
Hard
6.8