Basic linear amplifier base current question

"Substantially greater" is the proper formulation. If you use 12x the base current, it will work too. BTW, it is a multiple by 10, not a power of 10.

BR from Ivan

So is a power of ten a calculated value, or just a rule of thumb ("substantially greater than")? Thanks for your help!

The current should be 10X so that the base voltage remains the same and does not fall with rising Transistor current.

In the article on basic linear amplifiers, there is the following comment about the class A amplifier:

This means that R1 + R2 must burn at least 2.5mA (10 x Base current)

I'm confused about where the 10x base current comes from.  I'll freely admit that I'm a beginner with analog electronics, so this step is not obvious to me.  It'll probably be something very simple I should have thought of, but alas, I am at a loss.

That article is one of the clearest I've read about simple amplifiers, and I'm trying to understand every detail -- thanks for any help!