For this case we have an equation of the form:

Where,
A: initial amount
b: growth rate
t: time in years.
Substituting values we have:

By the time the population is triple we have:

Rewriting we have:

Clearing t we have:
Answer:
It will take for the population to triple about:
t = 73 years
Solution :
Amounts spent on a trip : $31.11, $25.01, $18.53, $14.37, $24.16, $21.91
Confidence interval = 80%
Average amount spent = 8 to 9 years old
One sample T confidence interval
μ : Mean of variance
80% of confidence interval results :
Using statistical software,
Variable : data
Sample mean : 22.515
Std. Err. = 2.3479945
DF = 5
L. limit : 19.049632
U. Limit : 25.980368
SD = 5.75
Critical value = 1.476