From Word Problems to Equations
Date: 01/28/99 at 22:46:54 From: Jeannie Weismann Subject: Algebra My daughter has come to me to get help in translating to an equation and solving the following problem: If the sides of a square are lengthened by 7 inches, the area becomes 121 inches squared. Find the length of a side of the original square. (I guessed the answer to be 4 but have no idea how to write the equation to solve the problem.) The problem before it has the answer in the back of the book, but shows no work, and we would like to know how to solve with showing work. That problem reads: If the sides of a square are lengthened by 3m, the area becomes 81m squared. Find the length of a side of the original square. The answer is 6. Please show me how to translate to an equation so I can help teach her how to do this. Thank you.
Date: 01/29/99 at 12:33:30 From: Doctor Peterson Subject: Re: Algebra Hi, Jeannie. Let's start with the preceding problem, and then I'll let you find your own solution. If the sides of a square are lengthened by 3m, we can call the original side length S (meters), and the new sides are (S+3). The area is the square of the side length, so our equation is (S+3)^2 = 81 (We write ^2 for an exponent of 2.) To solve this, we can take the square root of both sides to get S+3 = 9 Now we subtract 3 from both sides and get S = 6 Your problem is very similar, and your answer is right. It really doesn't take algebra to solve this one! - Doctor Peterson, The Math Forum http://mathforum.org/dr.math/
Search the Dr. Math Library:
Ask Dr. MathTM
© 1994- The Math Forum at NCTM. All rights reserved.