Having already discovered mathcad's rpm "unit" is radians per min and not rotations. I am having a new issue trying to figure out why I'm getting incorrect solutions for power.
This form works fine in Prime 8:
not sure where the .58 in the calculator of your screenshot stem from. Must be a wrong or very inaccurate approximation of pi?
EDIT: I just found the site with the calculator you used and it uses a factor 9.5488 which actually should be 60/(2 pi)=9.54929658...
rev=2pi not 1