HP 10bii+ Margin/Markup bug

[Rick314]

> The problem is CST/PRC/MU/MAR cannot be reduced to 1 formula (unlike TVM)

That is true Albert, but it is not a mathematical requirement. That is why I said "My guess is that this is because of the way the firmware is using the HP SOLVE app that is inside many of their calculators. They are not keeping track of all possibilities of what can be determined from the values provided."

> If user inputted CST, PRC, MAR, and wanted MU, what is it supposed to return ?

That isn't a real-world problem, whereas all cases in my list are. Try your example on the calculator, in the order given. After entering CST and PRC, enter MAR. Stop. What are you trying to do and what do you expect? MAR is determined from CST and PRC, so isn't then a valid input in addition to CST and PRC. Yet it is accepted without error by the calculator. So at that point you don't know what the calculator will use to calculate MU. You have an inconsistent (yet accepted without error) set of inputs. But it doesn't matter since entering CST, PRC, and MAR doesn't make sense.