Volume 4: Computations 1:- Although this is a volume for basic calculations, it is not to be taken lightly. The way that some of the topics are treated - with additional and atypical explanations makes use of methods and devices that might not be found anywhere else. Simple topics like ratios, foreign exchange and standard form are further simplified by unconventional approaches. The final topic - direct and inverse variation might be somewhat of a misfit because of its strong algebraic nature, but the calculation requirements keeps it in Volume 4.