Answer: a. 10.2 years
b. 12.6 years
c. 8.2 years
d. n = ln 4.1773/ln (1+r)
Step-by-step explanation:
$18,000 loan
annualend-of-year installment payments of $4,309
F = P(1+r)ⁿ
a. r = 15% = 0.15
18000 = 4309(1+0.15)ⁿ
18000/4309 = 1.15ⁿ
4.1773 = 1.15ⁿ
ln 4.1773 = ln 1.15ⁿ
ln 4.1773 = n*ln 1.15
n = ln 4.1773/ln 1.15
n = 10.2 years
b. r = 12% = 0.12
18000 = 4309(1+0.12)ⁿ
18000/4309 = 1.12ⁿ
4.1773 = 1.12ⁿ
ln 4.1773 = ln 1.12ⁿ
ln 4.1773 = n*ln 1.12
n = ln 4.1773/ln 1.12
n = 12.6 years
c. r = 19% = 0.19
18000 = 4309(1+0.19)ⁿ
18000/4309 = 1.19ⁿ
4.1773 = 1.19ⁿ
ln 4.1773 = ln 1.19ⁿ
ln 4.1773 = n*ln 1.19
n = ln 4.1773/ln 1.19
n = 8.2 years
d. The general relationship is n = ln 4.1773/ln (1+r) r as a decimal