not sure if this will help, memorising formulae which cover most of the weight& balance questions before sitting the test: (cant remember if these are right, check them first dont take my word for it!)
* forward limit of echo= (present wt-1360kg or whatever it is for the echo)x0.27 +2400mm
* time to PNR = (safe endurance x GS home) / 2xTAS
* distance to ETP = (total distance x GS home) / 2xTAS
* weight to move = (current weight x mm required to move) / arm from - arm to
*weight to add/subtract (rear limit) = (current weight x mm required to move) / rear CofG - arm to
*weight to add/subtract (forward limit) = use graph
these are all in the BobTait study books