We can set variables to solve this problem.
First, let's let the reciprocals be \( 1/x ,1/y \)
The arithmetic mean of the two numbers are \( [ 1/x + 1/y] / 2 = [ x + y] / [ 2xy]\)
This means the harmonic mean is \( [ 2xy] / [ x + y] \)
Now, we write an equation. Since the harmonic mean must eqaual 20, we set the equation up.
Now, we put x in terms of y. We have
\(2xy / [ x + y ] = 20 \\ xy / [ x + y] = 10 \\ xy = 10x + 10y \\ yx - 10y = 10x y ( x - 10) = 10x \\ y = 10x / [ x - 10]\)
I counted 7 numbers. Not sure if that's right.
Thanks! :)