(17B/19B) GPM: initial payment

[Gil]

Great!, but in a hurry we might not remember how to solve the problem so "simply" and — without checking with Excel, for instance — have doubts regarding the found result.

Of course, there are exceptions with some HP 12 calculator masters.

Thanks, Werner, for sharing this elegant insight.

PS
With more digit precision on my HP50G, I find ...70.

Regards,
GIL