Google Interview Questions Those Seems Weird To Me

Ques: How many golf balls can fit in a school bus?

Ans : This is one of those questions Google asks just to see if the applicant can explain the key challenge to solving the problem.

Reader Matt Beuchamp came up with a dandy answer, writing:

I figure a standard school bus is about 8ft wide by 6ft high by 20 feet long – this is just a guess based on the thousands of hours I have been trapped behind school buses while traffic in all directions is stopped.

That means 960 cubic feet and since there are 1728 cubic inches in a cubit foot, that means about 1.6 million cubic inches.

I calculate the volume of a golf ball to be about 2.5 cubic inches (4/3 * pi * .85) as .85 inches is the radius of a golf ball.

Divide that 2.5 cubic inches into 1.6 million and you come up with 660,000 golf balls. However, since there are seats and crap in there taking up space and also since the spherical shape of a golf ball means there will be considerable empty space between them when stacked, I’ll round down to 500,000 golf balls.

Which sounds ludicrous. I would have spitballed no more than 100k. But I stand by my math.

Of course, if we are talking about the kind of bus that George Bush went to school on or Barney Frank rides to work every day, it would be half that….or 250,000 golf balls

Ans : This is one of those questions where the trick is to come up with an easier answer than the one that’s seemingly being called for. We’d say. “$10 per window.”

Ans :We’d answer “However many the market dictates. If pianos need tuning once a week, and it takes an hour to tune a piano and a piano tuner works 8 hours a day for 5 days a week 40 pianos need tuning each week. We’d answer one for every 40 pianos.”

On Wikipedia, they call this a Fermi problem.

The classic Fermi problem, generally attributed to Fermi,^[2] is “How many piano tuners are there in Chicago?” A typical solution to this problem would involve multiplying together a series of estimates that would yield the correct answer if the estimates were correct. For example, we might make the following assumptions:

1. There are approximately 5,000,000 people living in Chicago.
2. On average, there are two persons in each household in Chicago.
3. Roughly one household in twenty has a piano that is tuned regularly.
4. Pianos that are tuned regularly are tuned on average about once per year.
5. It takes a piano tuner about two hours to tune a piano, including travel time.
6. Each piano tuner works eight hours in a day, five days in a week, and 50 weeks in a year.

From these assumptions we can compute that the number of piano tunings in a single year in Chicago is

(5,000,000 persons in Chicago) / (2 persons/household) × (1 piano/20 households) × (1 piano tuning per piano per year) = 125,000 piano tunings per year in Chicago.

And we can similarly calculate that the average piano tuner performs

(50 weeks/year)×(5 days/week)×(8 hours/day)×(1 piano tuning per 2 hours per piano tuner) = 1000 piano tunings per year per piano tuner.

Dividing gives

(125,000 piano tuning per year in Chicago) / (1000 piano tunings per year per piano tuner) = 125 piano tuners in Chicago.

A famous example of a Fermi-problem-like estimate is the Drake equation, which seeks to estimate the number of intelligent civilizations in the galaxy. The basic question of why, if there are a significant number of such civilizations, ours has never encountered any others is called the Fermi paradox.

Ans : So it doesn’t fall through the manhole (when the plane ordinarily flush with the plane of the street goes perpendicular to the street.)

Ans : He landed on Boardwalk. (Painful, right?)

Ans : Reader Hyloka nailed this one first: Take 6 of the 8 balls and put 3 on each side of the scale. If the heavy ball isn’t in the group of 6, you know it’s one of the remaining 2 and so you put those two in the scale and determine which one. If the heavy ball is in the 6, you have narrowed it down to 3. Of those 3, pick any 2 and put them on the scale. If the heavy ball is in that group of 2, you know which one it is. If both balls are of equal weight, then the heavy ball is the one you sat to the side.

Ans : The point here is to test the applicant’s ability to communicate complex ideas in simple language. Here’s our attempt, “A database is a machine that remembers lots of information about lots of things. People use them to help remember that information. Go play outside.”

Ans : This one is all about the judging interviewee’s creativity. We’d try to break the electric motor.

Ans : The maximum egg drops for this method is 14 times.
Instead of partitioning the floors by 10, Start at the 14th floor, and then go up 13 floors, then 12, then 11, then 10, 9, 8, 7, 6, 5, 4 until you get to the 99th floor, then here.  If the egg were to break at the 100th floor, it would take 12 drops (or 11 if you assume that it would break at the 100th floor).  Say, for example, that the 49th floor was the highest floor, the number of drops would be the 14th, 27th, 39th, 50th (the egg would break on the 50th floor) plus the 40, 41,42,43,44,45,46,47,48, and 49th floor for a total of 14 drops.

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