IN 20 MINUTES A DAY

PRACTICAL MATH SUCCESS

IN 20 MINUTES A DAY

Third Edition

®

NEW

YORK

Copyright © 2005 LearningExpress, LLC. All rights reserved under International and Pan-American Copyright Conventions. Published in the United States by LearningExpress, LLC, New York. Library of Congress Cataloging-in-Publication Data: Practical math success in 20 minutes a day.—3rd ed. p. cm. Rev. ed. of: Practical math success in 20 minutes a day / Judith Robinovitz. 2nd ed. ©1998. ISBN 1-57685-485-X 1. Mathematics. I. Robinovitz, Judith. Practical math success in 20 minutes a day. II. Title: Practical math success in twenty minutes a day. QA39.3.P7 2005 510'.7—dc22 2005040830 Printed in the United States of America 9 8 7 6 5 4 3 2 1 Third Edition ISBN 1-57685-485-X For information on LearningExpress, other LearningExpress products, or bulk sales, please write to us at: LearningExpress 55 Broadway 8th Floor New York, NY 10006 Or visit us at: www.learnatest.com

Contents

INTRODUCTION How to Use This Book PRETEST LESSON 1 Working with Fractions Introduces the three kinds of fractions—proper fractions, improper fractions, and mixed numbers—and teaches you how to change from one kind of fraction to another Converting Fractions How to reduce fractions, how to raise them to higher terms, and shortcuts for comparing fractions Adding and Subtracting Fractions Adding and subtracting fractions and mixed numbers and ﬁnding the least common denominator Multiplying and Dividing Fractions Focuses on multiplication and division with fractions and mixed numbers Fraction Shortcuts and Word Problems Arithmetic shortcuts with fractions and word problems Introduction to Decimals Explains the relationship between decimals and fractions Adding and Subtracting Decimals Deals with addition and subtraction of decimals, and how to add or subtract decimals and fractions together

v 1 13

LESSON 2

23

LESSON 3

31

LESSON 4 LESSON 5 LESSON 6 LESSON 7

39 49 57 67

v

– CONTENTS –

LESSON 8 LESSON 9

Multiplying and Dividing Decimals Focuses on multiplication and division of decimals Working with Percents Introduces the concept of percents and explains the relationship between percents and decimals and fractions Percent Word Problems The three main kinds of percent word problems and real-life applications Another Approach to Percents Offers a shortcut for ﬁnding certain kinds of percents and explains percent of change Ratios and Proportions What ratios and proportions are and how to work with them Averages: Mean, Median, and Mode The differences among the three “measures of central tendency” and how to solve problems involving them Probability How to tell when an event is more or less likely; problems with dice and cards Dealing with Word Problems Straightforward approaches to solving word problems Backdoor Approaches to Word Problems Other techniques for working with word problems Introducing Geometry Basic geometric concepts, such as points, planes, area, and perimeter Polygons and Triangles Deﬁnitions of polygons and triangles; ﬁnding areas and perimeters

77 87

LESSON 10 LESSON 11

95 105

LESSON 12 LESSON 13

115 125

LESSON 14 LESSON 15 LESSON 16 LESSON 17 LESSON 18 LESSON 19 LESSON 20

135 143 151 161 169

Quadrilaterals and Circles 181 Finding areas and perimeters of rectangles, squares, parallelograms, and circles Miscellaneous Math Working with positive and negative numbers, length units, squares and square roots, and algebraic equations 191

POSTTEST GLOSSARY APPENDIX A APPENDIX B Dealing with a Math Test Additional Resources

203 213 215 221

vi

How to Use This Book

his is a book for the mathematically challenged—for those who are challenged by the very thought of mathematics and may have developed calculitis, too much reliance on a calculator. As an educational consultant who has guided thousands of students through the transitions between high...