Dom,

A mathematician myself, I rely on "rules of Thumb" - If I hold my thumb up and can see the runway above my orthogonal directed index finger and, using the right hand rule, I then know that my hand is not on the right (correct) engine management tool.  After fixing that problem, if the houses are getting large too fast, I go around or go aground (depending).  Everything else is just a "feel good" estimate.

Scott Krueger (formerly know as "Crash")