Eulerian Trail

In graph theory, an Eulerian trail is a trail in a finite graph which visits every edge exactly once. Such Eulerian trail exists if : none of the vertex has an add degree (pen can start at any point) only two vertices have an odd degree (pen must start at one of the odd degree …

Pirate Riddle

100 coins to be distributed to 5 pirates: A, B, C, D, and E. Each person can set up a plan. Each pirate is smart, wants to stay alive, and wants to maximize profit. Each pirate will make a proposal. If the proposal does not get a majority vote or a tie, the pirate makes …

False Positive Riddle

1% of the rocks in the mine contain unobtanium. The device will always detect unobtainium if it is present. If a rock doesn't contain unobtanium, the device will give the correct reading 90% of the time. A rock with unobtainium sells for $1,000 but worthless without. A rock was unobtanium positive as detected by the …

Wizard Standoff Riddle

You are in a 3 way duel. Starting with you, you'll take turns casting spells to eliminate each other until one is remaining. No one can target 2 opponents on each turn, but each person can purposely miss. The 2nd opponent has 70% chance of turning his target into a fish. The 3rd opponent has …

Monty Hall Problem

Monty Hall Problem Suppose you're on a game show, and you're given the choice of three doors: Behind one door is a car; behind the others, goats. You pick a door, say No. 1, and the host, who knows what's behind the doors, opens another door, say No. 3, which has a goat. He then …

Boy or Girl Paradox

Boy or Girl Paradox, aka The Two Child Problem/Mr. Smith’s Children/Mrs. Smith Problem Mr. Smith has two children. The older child is a boy. What is the probability that his other child is also a boy? Mr. Smith has two children. At least one is a boy. What is the probability that his other child …