We have an investment that went from a initial value of PV = 1400 to a value of FV = 2177.36 in 71 months.
As the time is expressed in months, we assumed a monthly compounded interest, with a number of subperiods per year of m = 12.
Then, we have a total number of subperiods of n*m = 71.
We then can write the relation between the initial and final value as:
where r is the nominal rate.
We will calculate r as:
Replacing with the values we get:
We can now transformed this rate to an equivalent annually compounded rate as:
Answer: The equivalente annually compounded rate is 7.75%