Annual Percentage rate (APR) is calculated by the formula:
APR = 72i / {3P(n+1) + i(n-1)}
where:
i = Interest Rate
P = principal amount borrowed
n = number of months of the loan
Given:
Interest rate = $782.96
Principal amount = $4,000
number of months = 36 months
Substitute the given to the formula:
APR = 72(782.96) / [{3(4000)(36+1)} + {782.96(36-1)}]
APR = 56,373.12 / {444,000 + 27,403.60}
APR = 56,373.12 / 471,403.60
APR = .1196 X 100 ⇒ Multiply by 100 to get the percentage
APR = 11.96% or 12% (c)