Answer:
Step-by-step explanation:
The formula for compound annual interest is A = P(1 + r)t where
A = Accumulated or final amount (double $500 = $1000)
P = Principal or original amount ($500)
r = Rate as a decimal (0.08)
t = Time in years
1000 = 500(1 + 0.08)t
2 = 1.08t
Take the logarithm of both sides. I prefer the natural logarithm ln, but if you're more comfortable with base 10 logs they will work just as well
ln(2) = ln(1.08t)
ln(2) = t*ln(1.08)
t = ln(2)/ln(1.08)
t = 9.0065 years
Check: 500*1.089.0065 = $1000
