Basic Math and Pre-Algebra Workbook For Dummies, 2nd Edition

Chapter 5

Dividing Attention: Divisibility, Factors, and Multiples

In This Chapter

Testing numbers for divisibility without dividing

Understanding factors and multiples

Distinguishing between prime and composite numbers

Finding the factors and multiples of a number

Finding the greatest common factor and least common multiple

This chapter provides an important bridge between the Big Four operations earlier in the book and the topic of fractions coming up. And right up front, here's the big secret: Fractions are really just division. So, before you tackle fractions, the focus here is on divisibility — when you can evenly divide one number by another without getting a remainder.

First, I show you a few handy tricks for finding out whether one number is divisible by another — without actually having to divide. Next, I introduce the concepts of factors and multiples, which are closely related to divisibility.

The next few sections focus on factors. I show you how to distinguish between ...