Posted by sarah on .
I need help with this I keep putting the numbers in wrong on the formula ! PLEASE HELP
Price of article = $315.50
Down payment = $31.55
Monthly payment amount = $16.50
Duration of payments = 20 months
True annual interest rate to the nearest tenth = %
Formula: I(Interest)= 2YC/M(N+1)
y = payments per year; c = total interest paid; m = amount financed; n = total number of payments.

Math 
Ms. Sue,
Let's figure it this way.
315.5  31,55 = 283.95 >> amount financed
16.5 * 20 = 330 >> amount paid
330  283.95 = 46.05 >> interest
46.05 / 283.95 = 0.16217 = 16.2% >> interest rate 
Math Correction 
Ms. Sue,
Please ignore my previous post. I goofed!
I = PRT
46.05 = 283.95 * R * 1.6667
46.05 = 473.26R
46.04 / 473.26 = R
0.0972 = 9.7% = R