(11C) Loan Repayments - Printable Version +- HP Forums (https://www.hpmuseum.org/forum) +-- Forum: HP Software Libraries (/forum-10.html) +--- Forum: General Software Library (/forum-13.html) +--- Thread: (11C) Loan Repayments (/thread-11792.html) |
(11C) Loan Repayments - Gamo - 11-13-2018 01:37 PM Program to calculate for "Loan Repayments" n = number of payments i = Interest Rate in Percent PMT = Payment PV = Principal Formula Used: [attachment=6594] Procedure: Interest Rate [A] Principal [R/S] Payment [R/S] --> Answer Example: This Example is from HP-38C Owner's Handbook. Bill Buckskin wished to invest in a $22,000 log carbin to keep the rain off. A local merchant has offered to loan Bill the $22,000 at 10.5% interest. Making $200 monthly payments, how long will it take Bill to repay his mortgage? 10.5 [A] 22000 [R/S] 200 [R/S] --> 376.89 Answer: 376.89 // Months 12 ÷ Answer 31.41 // Years Program: Code:
Gamo RE: (11C) Loan Repayments - Albert Chan - 11-13-2018 03:09 PM (11-13-2018 01:37 PM)Gamo Wrote: This Example is from HP-38C Owner's Handbook. You might want to rearrange the order, to get more information from same calculation. 22000 [Enter] 200 / --> 110.00, number of payments if no interest 10.5 [R/S] --> 376.89, effect of 10.5% interest. 277 payments (23 years) just for interest ! RE: (11C) Loan Repayments - Gamo - 11-14-2018 05:20 AM Thanks Albert Chan Very good touch up. Gamo RE: (11C) Loan Repayments - Dieter - 11-17-2018 06:03 PM (11-13-2018 01:37 PM)Gamo Wrote: Formula Used: No, that's not the formula. The "1+i" part must be a subscript after the log, indicating that the base 1+i logarithm of the bracketed term is calculated. But the program uses a correct formula. I'd write it this way: \[\begin{align} n~&=~-log_{~1+i}~(1-\frac{i \cdot PV}{PMT}) \\ \\ &=~ -\frac{ln(1-\frac{i \cdot PV}{PMT})}{ln(1+~i)} \end{align}\] This is what the program correctly implements. Assuming that the user enters the monthly payment and the annual interest rate. Dieter |