Answer:
37.02%
Step-by-step explanation:
The formula of compound interest we will use is:

Where
FV is the future value [2,400,000 in this case]
PV is the present value [40,000 was invested]
r is the rate of interest per year (what we want to find)
t is the time in years [13 years]
Substituting and solving for r:
![FV=PV(1+r)^t\\2,400,000=40,000(1+r)^{13}\\60=(1+r)^{13}\\1+r=\sqrt[13]{60}\\ 1+r=1.3702\\r=0.3702](https://tex.z-dn.net/?f=FV%3DPV%281%2Br%29%5Et%5C%5C2%2C400%2C000%3D40%2C000%281%2Br%29%5E%7B13%7D%5C%5C60%3D%281%2Br%29%5E%7B13%7D%5C%5C1%2Br%3D%5Csqrt%5B13%5D%7B60%7D%5C%5C%201%2Br%3D1.3702%5C%5Cr%3D0.3702)
Thus, rate of interest was 37.02% (rounded to 2 decimal places)