Answer:
6%
Step-by-step explanation:
You want to know the interest rate that makes a £9000 investment have a value of £11362.29 after 4 years if interest is compounded annually.
Compound interest
The value of an account earning compound interest is given by ...
A = P(1 +r)^t
You want to know r when A = 11362.29, P = 9000, t = 4.
Solving the equation for r, we find ...
9000 = 11362.29(1 +r)^4 . . . . . . . . . . put the given values in the formula
9000/11362.29 = (1 +r)^4 . . . . . . . . . divide by 11362.29
(9000/11362.29)^(1/4) = 1 +r . . . . . . take the 4th root
r = (9000/11362.29)^(1/4) -1 . . . . . . subtract 1
r = 0.06 = 6%
Kamil's investment earned 6% interest.
