Google Interview Question: Estimate the rate of revoluti... | Glassdoor

Interview Question

Associate Product Manager Interview(Student Candidate) Mountain View, CA

Estimate the rate of revolution of the Earth.


Interview Answer

2 Answers


This is an Estimate question, that is clearly designed to stump the candidate. How do you react, when you get an astro physicist question without physics.

With any question - understand key terms:

What is revolution: Turns out its it the time the end goes around the sun ( once every yr)
Rate: its a measurement of something with respect to time ( what is the time frame) rate in hrs or minutes or year or day

You have to understand rotation vs Revolution. Most non physics majors will assume rotation. Earth's rotation around its axis is 1 day (24 hrs)

Rate = revolutions/time

We already have a starting rate which is equal to 1 rev/yr

Depending on the time frame given, the next step is to simply convert it to the time frame:

e.g rate of revoulution in a day. They are about 10 000 hrs in a yr so revolution is 1 rev/ 10000 hrs. In an interview you don t need to be accurate, actually they are about 8. K hrs in a yr. They are 24 hrs in a day so what would be the rate of rev in 24 hrs, less. Therefore the answer is 24/10 000 ~ = 25/10 000 = 1/400 rv in a day

Does this makes sense, yes the numer should be less than 1.

You can also go into what about a leap year and so forth. Key is to ask the definition of a revolution.

Anonymous on Oct 26, 2014

This question could also be just how do you even get one revolution per yr. You know Earth's rotation per day. How would you go about measuring the degrees in which the earth rotates in a day. In other words, you can't user your knowledge of 1 rev per yr. You have to arrive there.

Start here:

1) 24 hrs to rotate on its axis - we also know that to completely go around the sun, earth has to cover 360 degrees
2)how many degrees are in 24 hrs? We can measure this. Say its x.

By definition we know that it takes 360 degrees to go around the earth. 24hrs is equivalent to x degrees. where x< 360. So how many hrs is 360 degree is equivalent to: more. (360/x * 24 ) will give you the rate of revolution of the earth.

Anonymous on Oct 26, 2014

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