Welcome to MindCipher, a social repository of the world's greatest brain teasers, logic puzzles and mental challenges.
10 20 3 Coins
Not sure what the answer is, ideas welcome! You have 3 coins, one always comes up heads, the second always comes up tails, and the third is a fair coin. You select a coin at random. After selecting ...
Math help Submitted by city_slick
Easy
3.0
12 4 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
5 3 Sand Timer Puzzle
You have two sand timers with you. One can measure 7 minutes and the other sand timer can measure 11 minutes. This means that it takes 7 minutes for the sand timer to completely empty the sand from one ...
Submitted by Rohit Gurjar
Doable
5.0
16 1 100 Light Bulbs
There are 100 light switches, all of them are off. First, you walk by them, turning all of them on. Next, you walk by them turning every other one off. Then, you walk by them changing every third on ...
mathematical logical Submitted by Aakash
Hard
7.6
9 11 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
18 2 3 Men and a Hotel Room
Three men decided to split the cost of a hotel room. The hotel manager gave them a price of $30. The men split the bill evenly, each paying $10, and retired to their room. However, the manager real ...
Submitted by Valentin
Doable
4.2
8 8 Survivor
There are 1500 people sitting around a circular table. They are numbered in a regular manner (1 to 1500 along the table). Now, the 1st person gets a sword and kills the 2nd person. He then gives the s ...
Submitted by Shaheen
Hard
8.5
6 7 Binary 5 digits
What is the base 10 equivalent of the highest 5 digit binary number?
Easy
2.0
14 7 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 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 5 100 kg bag of potatoes
if you have a 100kg bag of potatoes, that are 99% water, they're left out in the sun and dry up a bit, so it's now 98% water, how heavy is the bag of potatoes?
Submitted by chuck3r
Doable
5.0
10 7 Sum of Two Prime Numbers
If p, q > 2 are consecutive in set of primes. Since p,q can only be odd number, (p+q) is an even number. Can (p+q)/2 be prime? from http://republicofmath.com/
Submitted by MoralMachine
Easy
3.2
2 2 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
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
9 9 1978
The year 1978 is such that the sum of the first two digits and the latter two digits is equal to the middle two digits, i.e. 19 + 78 = 97. What is the next year (after 1978) for which this is true?
Doable
6.6