This post is meant as a follow-up to an earlier article with the subject “Why are manhole covers round?“. It’ll feature some additional “Microsoft Hiring Questions”. Here are my personal “favorites” :
Riddles
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- You’ve got someone working for you for seven days and a gold bar to pay them. The gold bar is segmented into seven connected pieces. You must give them a piece of gold at the end of every day. If you are only allowed to make two breaks in the gold bar, how do you pay your worker?
- Answer
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- Imagine a disk spinning like a record player turn table. Half of the disk is black and the other is white. Assume you have an unlimited number of color sensors. How many sensors would you have to place around the disk to determine the direction the disk is spinning? Where would they be placed?
- Answer (Discussion)
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- You have two jars, 50 red marbles and 50 blue marbles. A jar will be picked at random, and then a marble will be picked from the jar. Placing all of the marbles in the jars, how can you maximize the chances of a red marble being picked? What are the exact odds of getting a red marble using your scheme?
- Answer
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- There is a room with a door (closed) and three light bulbs. Outside the room there are three switches, connected to the bulbs. You may manipulate the switches as you wish, but once you open the door you can’t change them. Identify each switch with its bulb. (note: For the Belgian & Dutch readers, this one was on “De Mol” a few years back.)
- Answer

Thinkers
- Interviewer hands you a black pen and says nothing but “This pen is red.”
- How are M&Ms made?
- You have been assigned to design Bill Gates bathroom. Naturally, cost is not a consideration. You may not speak to Bill.
- Suppose you go home, enter your house/apartment, hit the light switch, and nothing happens – no light floods the room. What exactly, in order, are the steps you would take in determining what the problem was?
Taken from:
Microsoft Interview Questions
The Answers (google cache)