It’s been a few years since I’ve used my HP calculators, and my RPN skills have atrophied. (I wanted to learn RPN in 2009.) Specifically, I don’t remember how to calculate probabilities with them. Specifically specifically, I want to calculate odds of winning various lottery games where you enter the number of numbers to be chosen from one field, and a number from another field. (I think I got the odds of correctly guessing all of the correct numbers in the first field, and then multiplied it by the number of choosable numbers in the other one.)
Can someone give me a step-by-step primer on how to do that on the HP32Sii and HP35S?
Since nobody has answered for a while, I’ll try to give direction. Note that I can’t help with the RPN, since I didn’t use it often.
The key that you want is the nCr button (looks like it is above the x key). The C is for combinations, which is what you want. So for the MegaMillions lottery, you are choosing 5 numbers out of a possible 75. What you want is 75C5. In order to figure out the RPN, just play with something where you know the answer.
For instance:
6C3 = 20
8C3 = 56
For help, the Excel function is COMBIN. A google of combinations should also be helpful. Be wary of combination’s friend, permutation, though.
Thanks. I have the formula written down somewhere (maybe even on this computer! Or the previous one), but I’d rather use a calculator function instead of figuring it out on paper. I’m lazy that way.
ISTR there’s a menu on one of the calculators, but I don’t remember it.