Answer:
See Below
Explanation:
This is a problem of compound interest. The formula is:
Where
F is the future value
P is the present value
r is the rate of interest
t is the time in years
P = 13,000
To double his money, that means, F = 26,000
a)
Now, r = 9% = 0.09, so time it takes:
So, its gonna take about 8.04 years to double
b)
Similarly, here we just use r = 0.06, so the calculation is:
So, its gonna take about 11.9 years to double
c)
Here, the r is 11% or 0.11
So, the time it will take:
So, it is going to take about 6.6 years to double
d)
The amount of time it takes to double his money decreases as the interest rate increases and the time increases as interest rate decreases.