Idiot\'s Guides Basic Math and Pre-Algebra

Chapter 4: Factors and Multiples 49 But how will you know when you’ve checked enough prime numbers? One way to tell is by com- p ...

50 Part 1: The World of Numbers CHECK POINT Decide if each number is prime or composite. If it’s composite, give a pair of facto ...

Chapter 4: Factors and Multiples 51 Let’s look at the prime factorization of 180 as an example. Start with any pair of factors o ...

52 Part 1: The World of Numbers Using Exponents Some prime factorizations are easy to write. The prime factorization of 42 is 2 ...

Chapter 4: Factors and Multiples 53 There are times when one of the numbers is the GCF of the two numbers. The GCF of 8 and 32 i ...

54 Part 1: The World of Numbers CHECK POINT Find the greatest common factor of each pair of numbers. 16. 18 a nd 42 42 and 70 1 ...

Chapter 4: Factors and Multiples 55 Instead, you’ll want to start by finding the prime factorization of both numbers. Let’s star ...

56 Part 1: The World of Numbers CHECK POINT Find the least common multiple of each pair of numbers. 14 and 35 45 and 105 286 an ...

CHAPTER 5 Fractions In This Chapter How to find equivalent fractions How to find common denominators Adding and subtracting fra ...

58 Part 1: The World of Numbers The Rational Numbers ........................................................................... ...

Chapter 5: Fractions 59 Because a whole number like 7 is a rational number, even though you wouldn’t usually think of it as a fr ...

60 Part 1: The World of Numbers Arithmetic with Fractions When you work with fractions, the methods of whole number arithmetic a ...

Chapter 5: Fractions 61 You can go the other way, too, taking a fraction to a simpler appearance. This is officially called simp ...

62 Part 1: The World of Numbers Dividing fractions introduces only one extra piece to the multiplication rule. To divide fractio ...

Chapter 5: Fractions 63 Multiply numerator times numerator and denominator times denominator, using the new numbers. MATH TRAP W ...

64 Part 1: The World of Numbers WORLDLY WISDOM To quickly convert a mixed number to an improper fraction, multiply the denominat ...

Chapter 5: Fractions 65 Suppose you want to subtract^13227. In order to do this operation, you need to make the denomina- tors o ...

66 Part 1: The World of Numbers For subtraction, it can be trickier, because there may be regrouping, or borrowing, involved. Tr ...

CHAPTER 6 Decimals In This Chapter The system of decimal fractions Writing very small num- bers in scientific notation Adding a ...

68 Part 1: The World of Numbers Decimal Fractions By now you’re familiar with the fractions that are called common, the ones wri ...