with a little ingenuity, logic and intuition.

At least the piano tuner problem involves estimations.
I heard it applied to how many piano tuners in a city. Assume a percentage of how many pianos are in the city, how often they need to be tuned, how long it takes to tune a piano, etc.
Take all these estimated factors into account to figure out how many piano tuners.

well, i think we can give diplomatic answers these questions. like for question “how many piano tuners are there in the world” answer is 203405320432 ( any random number), if interviewer needs proof then we can say " i have counted if you don’t believe you can count too"

For the windows I would also have asked if that included vehicle windows

They’re just trying to drive traffic to their search engine. The interview is a farce.

It would seem then that the real question is not just what estimate you came up with, its what the error bounds is when you’re done.

These are called fermi problems.
http://en.wikipedia.org/wiki/Fermi_problem

The answer to all of them should be “You should ask someone who is familiar with those types of problems, I’m a computer programmer”. Followed with a light slap of the person asking the question. If you attempt to glean information from the applicant’s answer, you are assuming you’re infinitely more brilliant than them.

But I’d bet answering the window washing question with something about installing Linux would gain you a few points.

For the windows one I would have to ask if the windows in Seattle really need washing. It rains almost all the time there.

Well, 1 can fit just fine. So would 100, or 1,000. The question isn’t asking for the maximum number, just generally “how many?”

I would charge what the competition charges, about $1 per window, I suppose. I might charge more based on the height of a building, since each building owner will be paying… Unless the mayor is paying? Besides, washing windows is a waste of my amazing logic skills!

Never enough piano tuners!

(For an exact answer, I definitely would Google!)

1. depends how big the bus is. and hey copter: did you account for seating, storage area, steering wheel, etc? the bus isn’t just an empty box.
2. it doesn’t matter how much you charge. buildings would constantly be getting knocked down, built up, getting re-dirtified. it would take an infinite amount of time and you would never get payed.
3. infinite. not only are there devices that tune pianos now, there are new, human piano tuners being born everyday.

For the golf ball question, I would say:
6 million, based on a bus being ~600inches long, ~100inches wide, and ~100inches tall. Which makes for 6 million cubic inches, and a golf ball is ~1×1×1 inches

I guess they are more looking for the logical reasoning behind your answer, more than the answer itself.