Question: John and Matt decide to play a game using a deck of cards. The game involves flipping two cards at a time. If both cards are black, they go into John’s pile and if both cards are red, they go into Matt’s pile. If one card is red and one card is black, they [...]
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11 Mar 10
Boxes of Money
Question: You are given b boxes and n dollar bills. The money has to be sealed in the b boxes in a way such that without thereafter opening a box, you can give someone a requested whole amount of dollars from 0 to n. How should b be related to n for this to happen? [...]
5 Mar 10
Chasing Dogs
Question: There are four dogs each at the corner of a unit square. Each of the dogs starts chasing the dog in the clockwise direction. They all run at the same speed and continuously change their direction accordingly so that they are always heading straight towards the other dog. How long does it take for [...]
2 Mar 10
Red and Blue Marbles
Question: You have 50 red marbles, 50 blue marbles and 2 jars. One of the jars is chosen at random and then one marble will be chosen from that jar at random. How would you maximize the chance of drawing a red marble? What is the probability of doing so? All 100 marbles should be [...]
26 Feb 10
Burning Sticks
Question: You have two sticks and matchbox. Each stick takes exactly an hour to burn from one end to the other. The sticks are not identical and do not burn at a constant rate. As a result, two equal lengths of the stick would not necessarily burn in the same amount of time. How would [...]
23 Feb 10
Trains and Birds
Question: A train leaves City X for City Y at 15 mph. At the very same time, a train leaves City Y for City X at 20 mph on the same track. At the same moment, a bird leaves the City X train station and flies towards the City Y train station at 25 mph. [...]
21 Feb 10
Globe Walker
Question: How many points are there on the globe where, by walking one mile south, then one mile east and then one mile north, you would reach the place where you started? Answer: The trivial answer to this question is one point, namely, the North Pole. But if you think that answer should suffice, you [...]
18 Feb 10
Clock Hands
Question: How many times a day do the minute and hour hands of a clock overlap? Answer: Did you think the answer was 24 times? Well if you did, it’s time you think again. Let’s do some math. In T hours, the minute hand completes T laps. In the same amount of time, the hour hand [...]
17 Feb 10
10 Google Interview Puzzles
Here is a list of 10 puzzles which have been asked on a Google Interview. They are not in any specific order. Is your husband a cheat? A certain town comprises of 100 married couples. Everyone in the town lives by the following rule: If a husband cheats on his wife, the husband is executed as [...]
15 Feb 10
The Ant Problem
Question: Three ants are sitting at the three corners of an equilateral triangle. Each ant starts randomly picks a direction and starts to move along the edge of the triangle. What is the probability that none of the ants collide? Answer: So let’s think this through. The ants can only avoid a collision if they [...]
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