Thanks rob!

I combined that with the rails helper 'number_with_delimiter, and it 
works great:

 def number_to_n_significant_digits(number, n = 3)
   ("%f"%[("%.#{n}g"%number).to_f]).sub(/\.?0*\z/,'')
 end

 #in my other method
 number_with_delimiter(number_to_n_significant_digits(number))

I don't think the 0.0000008 instead of 0.000000766 case will be a 
problem.

My next quest is to work out what's going on in your code snippet.
I can see that the sub at the end removes trailing zeros, right?

And the first part looks like some oldschool c-style string 
substitution, time to pull out the pickaxe :)

thanks again!
max
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