In this part . . .
Part III contains the "miracle math" chapters. Well, okay, the chapter about areas, perimeters, and volumes is only semimiraculous. But it's very handy and may be magical to some folks.
The big magic is in the power you get from the other chapters, those devoted to algebra (12), formulas (13), geometry (14), areas and volumes (15), and trigonometry (16). Those five concepts are powerful, and they usually inspire fear and awe when you first encounter them.
But consider this: Cave dwellers first feared fire because it could burn them. But when they mastered it, fire kept them warm and cooked their food. The modern equivalent is that when you master these subjects, your technical job will pay your heating bill and buy your groceries.