Two Gloves and Three Patients
You’re a surgeon in a remote clinic when three patients arrive requiring emergency operations. Supplies are running low—you rummage through the stockroom but...
Dice Corner
You’re looking through a hole at the corner of a standard die. The image below shows all you can see through the hole: portions of three faces meeting at the...
Coin Weighing 1
You’re the king of a massive empire. As a gift, a neighbouring kingdom has sent you 9 gold coins. Your advisor suspects that one of the coins is a forgery —...
Equal Shape Cutting 2
Cut the L-shape into 4 equal shapes of itself. The shapes can be rotated, but all 4 must be of the same size.
Equal Shape Cutting 1
Cut the triangle into 4 equal shapes of itself. The shapes can be rotated, but all 4 must be of the same size.
Measuring Time with Hourglasses 1
You’re making the perfect soft-boiled eggs: all you have to do is boil eggs in a pot of water for exactly 9 minutes. However, your kitchen timer is broken, and...
Two Children 1
You’re talking to your colleague at work when it comes up in the conversation that he has 2 children. “What genders are they?” you ask. “Well, I have at least...
Hummingbird
A train leaves Oakridge at 20 km/h, headed for Fairhaven. At the same time, another train leaves Fairhaven at 30 km/h, headed for Oakridge on the same track....
The Camel Race
An aging sheikh, nearing the end of his life, decides to leave his vast fortune to one of his two sons. To determine the heir, he devises a strange contest...
Taking Pills
After falling ill, Josh sees a doctor and is prescribed some medication. He is to take 1 pill of Xenoril and 1 pill of Yvexol every 24 hours. The two pills...
Marble Pairs
You’re given a jar containing 100 marbles, each one coloured either black or white, and there is at least 1 marble of each colour. You notice that if you pick...
Diagonals on a Cube
Two diagonal lines are drawn on a cube. What is the angle between these two lines?
Coins on a Table
You and a friend want to settle who is the smarter of you two with a game. The game is played on a circular table, with you and your friend taking turns to put...