# Exam Problem: Rounds per minute into Megabits per second

#### Ramses The Pharaoh

Hi, guys!
My exam comes in one week, so I need your urgent help
I found out, that one of the problems in the exam will be about convertion between rounds per minute (of a CD or HDD) and megabits per second (as reading speed). I have no idea what is the dependance between those two measures. Does anyone of you know a formula for convertion or have any clues how to derive such a formula.... Help?!

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#### WhirlwindMonk

You would need to find out how many megabits can be read in one revolution. Then it should be pretty easy, but without that information, I have a feeling this problem is impossible.

#### Ramses The Pharaoh

OK, if the question asks about how many megabits are read in one revolution, you say that "it should be pretty easy". Still, it is very foggy for me :-). Perhaps you could provide a small tip? ;)

#### HallsofIvy

Homework Helper
No, that's not what he said. he said you need to know how many bits can be read in one revolution. I presume that by "rounds per minute" you mean "revolutions per minute". Multiply that by "bytes read per revolution".

#### Ramses The Pharaoh

Hehe... nice point of view! :rofl:
However, this, being an exam problem, is assumed to be a little bit more complicated than simple arithmetics.
I think it is enough to know the radius, the angular velocity (or frequency) and the time to read one bit (or distance b/n bits)... Once having these variables, how should I combine the megabits and the revolutions?! This is my problem

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