My hp12c RPN problem

I am using RPN notation to calculate discounted interest. But I am getting incorrect results. Let me give simple example . 100 - 50/ 5^(4/2) I get result of 48 instead of 98. I am using y power x button. However the following works 100-50/5^2 Do you know what is my mistake? This is needed for calculating interest in the following way 100-25/(1.04)^(9/12)

Probably too many entries into the stack. You are losing the first one by the time you get to the last one. Try it this way: Calc 50/5^(4/2)=2 STO 1 100 Ent RCL 1 - That gets you 98.