You have 12 balls all look identical (in shape, color etc.). All of them have same weight except one defective ball. You don't know that the defective one is heavier or lighter than other balls. You can use a two sided balance system (not the … [Continue reading]

## River crossing

Three cannibals and three anthropologists have to cross a river. The boat they have is only big enough for two people. If at any point in time there are more cannibals on one side of the river than anthropologists, the cannibals will eat them. What … [Continue reading]

## King and wine bottles

A bad king has a cellar of 1000 bottles of delightful and very expensive wine. A neighboring queen plots to kill the bad king and sends a servant to poison the wine. Fortunately (or say unfortunately) the bad king's guards catch the servant after he … [Continue reading]

## Wires on fire

A guy has two wires of varying thickness, which each burns in 60 minutes. He actually wants to measure 45 mins. How can he measure 45 mins using only these two wires. (he can't cut the one wire in half because the wires are non-homogeneous and he … [Continue reading]

## Jelly beans

You have three jars that are all mislabeled. One contains peanut butter jelly beans, another grape jelly jelly beans and the third has a mix of both (not necessarily half-half mix). How many jelly beans would you have to pull out and out of which … [Continue reading]

## Bridge

Four friends A, B, C, D Need to cross a bridge.. A maximum of 2 people can cross at a time.. It is night and they have just 1 lamp. People that cross the bridge must carry the lamp to see the way.. A pair must walk together at the speed of … [Continue reading]

## Supersonic bee

Two trains enter a tunnel 200 miles long, traveling at 100 mph at the same time from opposite directions. As soon as they enter the tunnel a supersonic bee flying at 1000 mph starts from one train and heads toward the other one. As soon as it reaches … [Continue reading]

## Palindrome dates

This year on October 2, 2001, the date in MMDDYYYY format will be a palindrome (same forwards as backwards). 10/02/2001 When was the last date that this occurred on? … [Continue reading]

## Daughter’s ages

Two MIT math grads bump into each other at Fairway on the upper west side. They haven't seen each other in over 20 years. The first grad says to the second: "how have you been?" Second: "great! i got married and i have three daughters now" First: … [Continue reading]

## Red and blue marbles

You have two jars, 50 red marbles and 50 blue marbles. You need to place all the marbles into the jars such that when you blindly pick one marble out of one jar, you maximize the chances that it will be red. When picking, you'll first randomly pick a … [Continue reading]