Question

What is the rate of interest charged if a 9 month loan of $1200 is paid off with with $1312.50?

Answer 1

P = Po + Po*r*t = $1312.50
1200 + 1200*(r/12)*9 = 1312.50
900r = 1312.50 - 1200 = 112.50
r = 0.125 = 12.5% APR.