How do I solve the question
A company’s sales just finished 8 years of consecutive growth, they are now 2x the amount 8 years ago. What is the CAGR?
I guess I should do it like this
$$ K_0 \cdot (1 + r)^8 = 2 \cdot K_0 \Leftrightarrow (1 + r)^8 = 2 $$
but I don't know what to do with the exponent of 8. I guess I could say
$$ (1 + r)^8 = 2 \Leftrightarrow 1 + r =2^\frac{1}{8} \Leftrightarrow r = 2^\frac{1}{8} - 1, $$
but I have no idea how to calculate $2^\frac{1}{8}$, so I assume there is an easier way.
Is it btw correct to use $2^\frac{1}{8}$ rather than using some logarithmic function (I just can't remember how)?