The formula is an example of exponential growth with base 1.09.
Determine an equivalent continuous growth formula using base .
Also, what if it asks me to use a different base?
Suppose we wish to change to base
Instead of , we want , where is a constant to be determined.
We have: .
Take logs (base ): .
. . Hence: .
If we want to write as an exponential with base b, we have, as Soroban said, . Now take the natural logarithm of both sides: and so the equation becomes and .
The advantage is that your calculator has a "ln" key but not a " " key!
In particular, if b= e, then ln(b)= 1 so and .
If b= 2, then ln(b)= ln(2)= 0.6931 so and .