math
posted by jim on .
You invest 3400 into account earning simple intrest. The balance is 4624 after 8 years. What is rate of intrest?

4624 = 3400(1+i)^8
(1+i)^8 = 1.36 take the 8th root of both sides
1+i = 1.03918
i = .03918 or 3.9% 
We use the formula:
M = P( 1 + i )^n
M is the final amount including the principal.
P is the principal amount.
i is the rate of interest per year.
n is the number of years invested.
M = 4624
P = 3400
n = 8 years
We seek i.
4624 = 3400(1 + i)^8
You do the rest.