An animal reserve has 40,000 elk. the population increases 11% a year. how long tell the population is equal to 80,000

Initial amount: 40,000
Annual growth rate 11%
Need to reach 80,000 elks in n years:

P=A(1+r)ⁿ
80,000 = 40,000(1+0.11)ⁿ
80,000 = 40,000(1.1)ⁿ
Divide both sides by 40,000
2 = (1.1)ⁿ
ln(2) = n.ln(1.1)
0.693147 = n.(0.09531)
and n = 0.693147/0.09531
n = 7.27 years

The answer to your question is d 68%