Answer:
7.615%
Explanation:
we can use the present value of an annuity formula to determine the interest rate:
present value of an annuity due = (payment / i) x (1 + i) x {1 - [1 / (1 + i)ⁿ]}
80,000 = (15,500/ i) x (1 + i) x {1 - [1 / (1 + i)⁷]}
1 - [1 / (1 + i)⁷] = 80,000 / [(15,500/ i) x (1 + i)]
1 - 80,000 / [(15,500/ i) x (1 + i)] = 1 / (1 + i)⁷
(1 + i)⁷ = 1 / {1 - 80,000 / [(15,500/ i) x (1 + i)]}
(1 + i)⁷ = 1 / {[(15,500/ i) x (1 + i) - 80,000] / [(15,500/ i) x (1 + i)]}
1 + i = ⁷√(1 / {[(15,500/ i) x (1 + i) - 80,000] / [(15,500/ i) x (1 + i)]})
1 + i = ⁷√(1 / {[1/i - 64,500] / [(15,500/ i + 15,500)]})
...
after a lot of complicated math,
1 + i = 1.07615
i = 0.07615 = 7.615%
