Answer:
11.7%
Step-by-step explanation:
The account balance (A) for a principal amount P and monthly interest rate r will be ...
A = P(1 +r)^8
Then we can divide by P and take the 8th root to find r:
A/P = (1+r)^8
(A/P)^(1/8) = 1 +r
(A/P)^(1/8) - 1 = r
Since this is the monthly rate, we need to multiply this value by 12 to find the annual interest rate on the account:
annual rate = 12((A/P)^(1/8) -1) = 12((9779/9047)^(1/8) -1) ≈ 0.11728 ≈ 11.7%
