A quick reply as its beeroclock
All aviation maths is no more complicated than year 9 maths this includes all fuel, time and navigation problems, this is so for VFR, IFR and space shots I think.
A simple elegant solution for amended MDA is:
A. Determine new climb gradiant ROC/GS
B. Determine new MDA MDA + HD-(NCG/DCG*HD), where;
ROC = RATE OF CLIMB ft/min
GS = GROUND SPEED knots
Prove the above by using unity brackets, it works
HD = HEIGHT DIFFERENCE between MDA and final MAP height
NCG = NEW CLIMB GRADIENT
DGG = DESIGN CLIMB GRADIENT
Draw a little geometry, it works, its simple and you can do it in your head
Schmacko