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 TOPICS This page:   algebra    Search   Dr. Math See also the Dr. Math FAQ:   order of operations Internet Library:   basic algebra T2T FAQ:   algebra help MIDDLE SCHOOL About Math Algebra    equations    factoring expressions    graphing equations Arithmetic    division    exponents    factorials    factoring numbers    fractions/percents    logarithms Definitions Geometry    2-dimensional      conic sections/        circles      triangles/polygons    3D and higher      polyhedra History/Biography Logic Measurement    calendars/      dates/time    temperature    terms/units Number Sense    factoring numbers    negative numbers    pi    prime numbers    square roots Probability Puzzles Ratio/Proportion Statistics Word Problems Browse Middle School Algebra Stars indicate particularly interesting answers or good places to begin browsing. Selected answers to common questions:     Direct and indirect variation.     Inequalities and negative numbers.     Positive/negative integer rules.     Solving simple linear equations. Why Does Cross Multiplication Work? [05/09/2002] Why does the rule a/b = c/d also mean ad = bc? Why can we solve proportions by cross multiplying? Why Does Long Division Work? [12/22/2006] I'm curious why the standard long division algorithm works. How do all the "bringing down" and other steps lead to the right answer? Why Does the Order of Square/Square Root Matter? [8/28/1996] Why does the square root of x^2 equal absolute value of x, but the square of the square root of x equals just plain old x? Why Do We Have the Order of Operations? [03/05/2006] Why do we have the order of operations? Why can't we just calculate from left to right? That seems much easier and more logical to me. Why do we Need Algebra? [9/13/1996] Why do we need algebra? Why Do We Use Variables in Algebra? [01/31/2004] Why do we use letters to represent numbers in algebra? Why Factor? [08/18/2001] I've been explained the how's, the where's, the what's, but not the WHY. What is the practical use of factoring? Why Flip the Inequality Sign? [10/26/2001] Please tell me why you flip the inequality sign when dividing by a negative number. Why FOIL? [11/21/2002] How can I explain to the class the importance of learning FOIL? The Why of Algebra [11/13/1998] What is algebra for? Why do you need the letters and variables? Why Order of Operations? [5/17/1995] 7th-graders wonder why we use the order of operations at all. Why not just set up problems to read from left-to-right? Can you suggest some "real-life" examples that show the necessity of using the order of operations? Why Some Solutions to Absolute Value Equations are False [10/24/2004] When solving equations involving absolute value, you sometimes get an answer that doesn't check in the original equation. What is it about absolute value that makes this happen? Why Use Letters in Math? [12/01/1999] Why do we need to use letters in math? Why Use n for Any Number? [09/28/2002] Why do people use n when any number can fit in or when they want to indicate position? Why Use Variables? [06/01/1999] What is the point of using variables when you could use numbers? Why Use X and Y for Variables? [10/23/2002] Why do we use x and y for variables in an equation? Writing Equations for Word Problems [09/01/1998] Can you help me convert the following word problems to equations and solve them? An oil painting is 16 years older than a watercolor .... x - 8 = -5 [06/13/2001] I know the answer but our teacher wants us to show all of our work and add something to both sides. Young's Formula [08/21/1999] Calculating a child's dose of medicine based on the adult dose. Page: [

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