Why are problems known in Calculus I as “doubling and halving functions” base e, and not base 2? If you are unfamiliar with this name, these problems typically involve populatin growth, interest rates, or half-lives. Sometimes, the half-live problems are known as decaying functions, which is a more general term…
Just wanted to hear the Straight Dope on this…
Mathematicians use e for just about everything 
Seriously, anything involving calculus is a lot easier written as e[sup]ln2 . x[/sup] than as 2[sup]x[/sup] because the first can be differentiated in your sleep (ln2 . e[sup]ln2 . x[/sup]).
I don’t know what you’re specifically discussing; maybe a better question is why they’re doubling rather than ‘multiplying by e’
Exponential growth might be at rates other than doubling or halving.
Many studies are done algebraically, so the base 2 or base 10 isn’t signnificant in the formulas.
Sorry…this was supposed to be in General Questions! Oops!
Maybe a moderator can come along and help me re-file this thread on the correct board!
Oh, bother!
As others have stated, there’s no reason why you can’t use base 2, or base 3, or base anything. The only thing is, exp is very easy to integrate and differentiate. For any other exponential function, you have to convert it to base e in order to do calculus on it.