Calculating Beat Frequency of 3 Frequencies

[tomcs]

Homework Statement

If there are three frequencies: 200hz, 206hz and 209hz, how do you calculate the beat frequency of three frequencies?

Homework Equations

Fb=abs(F1-F2)

The Attempt at a Solution

 

[Astronuc]

See if this helps - http://hyperphysics.phy-astr.gsu.edu/hbase/sound/beat.html

http://hyperphysics.phy-astr.gsu.edu/hbase/audio/sumdif.html#c1

What are the possible combinations?

 

[tomcs]

thanx for the links but still not sure how to solve it...
Can you clarify what you meant by 'possible combination?'

thanx a lot