Brain Teasers & Logic Puzzles

A farmer needs to transport a wolf, a goat, and a cabbage across a river in a boat. The boat can only hold the farmer and one other item. The wolf cannot be left alone with the goat, and the goat cannot be left alone with the cabbage. How can the farmer safely get all three items across the river?

Four people need to cross a rickety bridge at night. They have only one torch, which must be used for every crossing. The bridge can only support two people at a time. The four people cross at different speeds: one takes 1 minute, one takes 2 minutes, one takes 5 minutes, and the slowest takes 10 minutes. When two people cross together, they move at the speed of the slower person. What is the minimum time required for all four to cross?

Three married couples must cross a river using a boat that can only hold two people at a time. The challenge is that no wife can be on a bank or in the boat with another man unless her own husband is also present. How can all six people cross the river?

Three missionaries and three cannibals must cross a river. The boat can hold at most two people. The constraint is that for any bank, and in the boat, if there are missionaries present, they cannot be outnumbered by cannibals (or they will be eaten). How can everyone cross safely?

You have two hourglasses: one that measures exactly 7 minutes and another that measures exactly 11 minutes. Using only these two hourglasses, how can you measure exactly 15 minutes?

You are given two ropes and a lighter. Each rope takes exactly 60 minutes to burn from one end to the other, but they burn at a non-uniform rate (e.g., the first half might take 50 minutes and the second half 10 minutes). How can you measure exactly 45 minutes?

You have 10 bottles of pills. Nine of the bottles contain pills weighing 10 grams each, but one bottle contains pills that are all 11 grams each. You have a digital scale that you can use only once. How can you find the bottle with the heavier pills?

You have 12 identical-looking coins. One of them is counterfeit and is either slightly heavier or slightly lighter than the others. Using a simple balance scale only three times, how do you find the counterfeit coin and determine if it's heavier or lighter?

You are in a 100-story building and are given two identical eggs. You need to find the highest floor from which an egg can be dropped without breaking. What is the minimum number of drops you need in the worst-case scenario to guarantee you find this floor?

You are in a room downstairs with three light switches, each corresponding to one of three light bulbs in a room upstairs. You can flip the switches as much as you want, but you are only allowed one trip upstairs to the room with the bulbs. How can you determine which switch controls which bulb?

You are at a fork in the road. One path leads to safety, and the other to danger. There are two guards, one at each path. One guard always tells the truth, and the other always lies. You are allowed to ask only one yes/no question to one of the guards to find the safe path. What question do you ask?

A digital seven-segment display is supposed to show the number 8, which uses all seven segments. However, one of the seven segments is broken and will not light up. What number could the display be showing?

You are on an island inhabited by two types of people: Knights, who always tell the truth, and Knaves, who always lie. You meet two islanders, A and B. Islander A says, "At least one of us is a Knave." What are A and B?

A group of 100 people, all perfect logicians, are on an island. They are all blue-eyed, but no one knows their own eye color. They are forbidden from communicating about eye color. An outsider makes a public announcement: "I see at least one person with blue eyes." Knowing that everyone is a perfect logician, what happens?

You're on a game show with three doors. Behind one is a car; behind the others, goats. You pick a door (say, Door 1). The host, who knows what's behind the doors, opens another door (say, Door 3) to reveal a goat. He then asks if you want to switch your choice to Door 2. Should you switch?

This is a classic cryptarithmetic puzzle. Each letter represents a unique digit from 0 to 9. The mapping must be consistent (e.g., if 'E' is 5, it's 5 everywhere). What is the solution to the equation SEND + MORE = MONEY?

Using the numbers 3, 3, 8, 8 and the standard arithmetic operations (+, -, ×, ÷) and parentheses, find a way to make 24.