Subtraction is dealt with in equations, and the chapter concludes with work focusing on lines, angles, and the Triangle Sum Property. This chapter features two themes. The second theme is transformations. Division, the latest of the fundamental operations to be studied in this book is by no means the least important. Rate and ratio comparision, the two principal uses for division, have applications throughout matheamtics.
Proportions are also of fundamental significance.
There are many applications of proportions, arising naturally from both rates and ratios, including geometry applications to similar figures. Problems dealing with fractions are found throughout the chapter, whole fractions yielding infinite repeating decimals are addressed. The unifying idea of this chapter is area. Work with area of right triangles and the Pythagorean Theorem as well as area of trapezoids. Students are also introduced to square roots and they eventually work with irrational numbers and pi.