Welcome to MindCipher, a social repository of the world's greatest brain teasers, logic puzzles and mental challenges.

Filtered by tag: geometry

9 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
5.7
9 1 Mutilated Chessboard Problem
Suppose a standard 8×8 chessboard has two diagonally opposite corners removed, leaving 62 squares. Is it possible to place 31 dominoes of size 2×1 so as to cover all of these squares?
geometry chess proofs Submitted by Ravi
Hard
7.1
7 7 The Famous Hole in a Sphere
This incredible problem was first made famous by Martin Gardner with his ‘Mathematical Games’ column published in Scientific American throughout the 60s and 70s. A cylindrical hole, 6 inches long, ...
Math Lateral geometry Submitted by Ravi
Hard
6.7
6 4 Bug's Eye
You are a bug sitting in one corner of a cubic room. You wish to walk (not fly) to the extreme opposite corner – the corner furthest from you. Describe the shortest path that you can walk.
geometry trigonometry Submitted by Ravi
Doable
3.8
4 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
2.8
2 2 The North Pole Bear Puzzle Reloaded
A man walks 1 mile south, then 1 mile east, and finally 1 mile north to find himself in exactly the same position as he started. He is NOT at the north pole, nor does he shoot a bear. Where is he? ...
brain teaser geometry Submitted by Ravi
Doable
6.0