50g

There is one function that is very useful in your HP 50g, it is the XQ 
function; in RPN after you get a result that comes in decimal form, 
press X [ALPHA] Q [ENTER] the function look for a fraction form for 
that number, a combination of a fraction and PI or a irrational form 
like square_root(1/2). So go ahead a experiment with that function.