Question 1146553
P=Po(a^t)
26000=11000(1.018)^t
2.3636=1.018^t
ln 2.3636=t ln 1.018 but carry all digits through and round at end

t=ln 2.3636/ln 1.018
=48.22 years or 48 years
This is a little more than doubling, so rule of 72 would say a little more than 72/1.8=40. Answer makes sense.