Welcome to MindCipher, a social repository of the world's greatest brain teasers, logic puzzles and mental challenges.
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
6 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
8 8 Prisoners and hats
100 prisoners are standing in a line each 1 seeing the back of the ones in front of him. Each prisoner is given a black or a white hat. If they can guess the color of their hat they can go away freel ...
logic brain teaser Submitted by Valentin
Hard
8.5
5 6 12 balls part 2
You have 12 identical RUBBER balls each of 10 grams and one of 9 grams.You have three weighs of a weighing machine (not a balance scale) to determine which ball is different and whether it is heavier o ...
Submitted by Vishal barot
Doable
3.3
3 5 Brain Teaser 56
Answer Yes or No to this brain teaser
Easy
2.8
8 3 The Tallest Mountain
A man approaches you with a very enigmatic look on his face. He asks your for a bit of your time and if you could answer a quick question for him. He asks: “Before Mt. Everest was discovered, which w ...
riddle Submitted by Ravi
Easy
2.3
11 4 Measuring Up
You have a 3 and a 5 litre water container, each container has no markings except for that which gives you its total volume. You also have a running tap. You must use the containers and the tap in su ...
logic brain teaser Submitted by Ravi
Easy
3.1
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
7 8 Clock Works - 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?
Easy
3.1
7 5 Burning Rope
There are two lengths of rope. Each one can burn in exactly one hour. They are not necessarily of the same length or width as each other. They also are not of uniform width (may be wider in middle th ...
Submitted by Ravi
Doable
4.3
10 4 Two Trains
Two trains (Train A and B) with 200 km between them are travelling towards each other at 100km/h. A mosquito, initially standing on the front of Train A, starts travelling towards Train B at 150km/h. O ...
Math physics rates Submitted by Ravi
Doable
4.5
6 7 Death by drawing?
You are a prisoner in a strange foreign land, and a random drawing will decide your fate. You are given 2 bags, 10 white marbles, and 10 black marbles. You are to place the marbles in the bags in any a ...
probability Submitted by Gene
Doable
5.0
4 3 The Middle of Nowhere
What is in the middle of "nowhere"? The answer is indisputable, and not based on some philosophy.
riddle Submitted by Aakash
Easy
2.4
8 10 Interview Question - Databases
This is a common interview question at companies like Google and Amazon: “Explain a database in three sentences to your eight-year-old nephew.” This question has an infinite number of solutions. Fee ...
Easy
2.7
6 10 Happy Handshaking
Jack and his wife went to a party where four other married couples were present. Every person shook hands with everyone he or she was not acquainted with. When the handshaking was over, Jack asked ev ...
Submitted by Valentin
Hard
8.0