# RPN mode

I tried the following using my HP calculator 54 1400 40 % Got 560 Hit / Got 2.5 My expected value is 54/560= 0.09643 Is it because Calculator not removing 1400 from stack? How do you use RPN for this type of problem? I am worried if I get into any similar problems, if I use RPN notation. Appreciate if you have any tips on similar mistakes.

If you just input: 54 1400 .40 then , you will get the right answer. When you use the % key it doesn’t lock the answer into the stack.

RPN mode was invented by God himself. We were forced to use RPN mode in my analyst training–I was so pissed! By the beginning of week 2, I couldn’t believe I ever used a non-HP, non-RPN calculator.

kkent Wrote: ------------------------------------------------------- > RPN mode was invented by God himself. We were > forced to use RPN mode in my analyst training–I > was so pissed! By the beginning of week 2, I > couldn’t believe I ever used a non-HP, non-RPN > calculator. Yeah I’ve read that users of it love it (most of them), but why? Care to elaborate? Thanks.

It’s incredible how fast you can calculate. I forgot the word, but the calculator “stacks” numbers, so you never have to write answers down in order to continue with a calculation. You can calculate this: (((9X2)^6))-(66+4)(-7))/((12^-2)-56)^.5 without ever having to write down an answer. You could literally calculate this entire weird equation in 10 seconds or less; this calculation would take 45 seconds to do in alebraic mode. I’ve seen far more complicated equations that can be done in 20 seconds using RPN and about 4 minutes using the alebraic mode. But even with everyday use, as your brain adjusts to the non-intuitive nature of the calculator, it becomes like typing. Once the brain has adjusted, it’s the fastest system of calculation, bar none. Since quitting my job 2 months ago and studying for the L2 CFA exam, I’ve been using my TI BAII Plus. Even today, I still find myself typing in RPN mode sometimes because it now seems so intuitive (The HP I learned on isn’t allowed for the exam–some other HP is, but I passed L1 with the TI, so if it ain’t broke, don’t fix it). I honestly think the world is missing out by keeping itself in the algebraic box.

Sounds pretty awesome to me and it seems very practical to know. I’m surprised you didn’t just get the other HP for writing L2, but I hear you. I wouldn’t change a thing if the TI worked for you on L1. I ended up buying the TI BA II plus pro mainly because I didn’t want to go through the hassle of having to learn RPN, but it definitely intrigues the hell out of me. Thanks for the explanation. Maybe I’ll try to learn it one of these days.

Except the right way to do calculations isn’t either of those. It’s on a PC where you can see and edit the calculation you just did. My cell phone has significantly more computer power than the computers I used to use to teach Mathematica… CFAI needs to fix this anachronism of sending you into the exam hobbled like you won’t be in your jobs. I think they should allow laptops in the exams (or provide them). Even if you put all of the literature on your laptop, how much are you going to learn in the exam? (none) You can also make a significantly more demanding and real-world test then. On the exam, youare answering questions about por-forma accounting statements without a spreadsheet, answering derivatives questions without basic derivatives software, bond questions without something that does much bond math (will either of those calculators give you convexity or duration?), etc… I haven’t used a calculator in 15 years except on the stupid CFA exams.

Joey, I fundamentally agree with you, but at my old job, often times those who actually had client contact would have to carry around their HPs because clients would ask them math questions on the phone or in person. They’d just whip out the HP and bingo. So in some rare instances, I guess it can help (but I pretty much agree with you). somewhat, I guess I just figured that there aren’t weird/long enough calculations on the CFA exam to justify me putting up another \$30-\$40 (cheapest person alive? Right up there).

I don’t want any of the sales people I have ever met doing any math problems.

Not salespeople, investment banking managers.

Ah. You mean those guys who wear neckties and socks. I tried to find some socks the other day and I think I don’t own a single pair of socks.

JoeyDVivre Wrote: ------------------------------------------------------- > Ah. You mean those guys who wear neckties and > socks. I tried to find some socks the other day > and I think I don’t own a single pair of socks. Pantyhose?

Well, not exactly. Fishnet stockings with garters. But usually just when I’m alone.