Been reading some Microsoft Interview questions. They’re interesting, that’s for sure. I’ve heard that they no longer use logic questions since they don’t really signify a good employee.

However, I hate how there is no ‘expected’ answers. While I don’t mind doing them on my own, I like seeing how others answer. Kind of like the college submission essay where the student applicants had to answer the question, “Is this a question?” I think the ‘winning’ answer was, “Yes, if this is an answer.”

Anyway, it’s like 5:30am, and I should get some sleep.


Some of my answers though:

  • Why is a manhole cover round? Because manholes are round. It would be silly to have square manhole covers when the manholes were round! Also, since it’s not possible to fall into the hole. Since they’re easy to move (rolling them on their side). Also, they’re easier to install since there is no orientation requirements.
  • How many cars are there in the USA? (A popular variant is “How many gas stations are there in the USA?”) Too many.
  • 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. Easy. Turn on one light for a minute or so. Then turn it off and turn on another light. Enter the room. The lit light is the currently turned on switch. The switch that was turned on is found simply by seeing which unlit bulb is warm.
  • Suppose you had 8 billiard balls, and one of them was slightly heavier, but the only way to tell was by putting it on a scale against another. What’s the fewest number of times you’d have to use the scale to find the heavier ball? Split them up into three groups (3, 3, 2) Weight the two groups of three. If their even, it’s one of the two, and a simple check will show the answer. If one side is heavier, make another group of three and weight one ball on each side. If one of them is heavier, it’s the one, otherwise it’s the one to the side. So in short, the answer is two times.
  • You have 4 jars of pills. Each pill is a certain weight, except for contaminated pills contained in one jar, where each pill is weight + 1. How could you tell which jar had the contaminated pills in just one measurement? Take one pill from the first, two from the second, three from the third, and four from the fourth. Weight them once, and then (1x + 2x + 3x + 4x) – 10 = Jar Number
  • If you had an infinite supply of water and a 5 quart and 3 quart pail, how would you measure exactly 4 quarts? Another easy one. Fill the 3 quart pail, pour into the 5 quart. Fill the 3 quart again, and fill the 5 quart until full. This will leave 1 qt in the pail. Dump out the 5 quart and put the 1 quart you have saved in it. Add another full 3 qt to acheive 4 qts.
  • You have a bucket of jelly beans. Some are red, some are blue, and some green. With your eyes closed, pick out 2 of a like color. How many do you have to grab to be sure you have 2 of the same? If you pick three, it’s possible they could all be different colors, so the only possible way to be SURE that at least two are alike, would be to pick four.
  • Multiple by 8 without using multiplication or addition. Now do the same with 7. I love bitwise manip: x << 4 and (x << 4 - x) (It's programming stuff, if you don't understand, don't worry about it.)
  • Interviewer hands you a black pen and says nothing but “This pen is red.” I’m sorry, the application says that I can only use blue or black pens. Besides, my parole officer says I can’t handle sharp objects
  • About Matthew Jones

    Writer, Programmer, Astronomer, Dreamer, Wisher, Fighter. Always striving to be better than I was.
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