Using Common Denominators to Compare Fractions
Date: 03/17/98 at 20:37:56 From: Tasha Thompson Subject: pre-algebra Here are the directions: write <, >, or = for each blank. Use equivalent fractions to decide. Here's an example: 3/8 ___ 4/9 I can't figure out how to do it. Can you tell me the answer and show me how you got it?
Date: 03/18/98 at 11:23:17 From: Doctor Johnny Subject: Re: pre-algebra Tasha, Hello there. My name is Dr. Johnny, and I am going to try to help you compare fractions. There are several ways that you can compare fractions, but since you have expressed an interest in using equivalent fractions, that is what I will try to explain. Before we discuss how to compare fractions, we must answer the question: "What is an equivalent fraction?" Equivalent fractions are fractions that, although they have different numbers, they have exactly the same value. The first thing that you must do is consider a common denominator (what will both denominators go into?). If you cannot see what both denominators will go into, a common way to find a common denominator is to multiply the two denominators together. NOTE: This may not be the least common denominator, but it is a common denominator that will serve the same purpose. 3 4 - - A common denominator is 72, which is 8 times 9. 8 9 Now that you have a common denominator, you must concentrate on renaming the fraction. To do this, you must use division and multiplication. 3 27 - = ---- Divide 8 into 72. Multiply the answer by 3. This renames 8 72 the fraction. 4 32 - = ---- Divide 9 into 72. Multiply the answer by 4. This renames 9 72 the fraction. Now that you have the fractions with the same denominator, all you have to do is compare the numerators 27 and 32. Since 27 < 32, the fractions can be compared in the following manner: 27 32 -- < -- 72 72 So you can say that 3 4 - < - 8 9 I hope that this explanation will help you better understand how to compare fractions by using equivalent fractions. -Doctor Johnny, The Math Forum Check out our web site! http://mathforum.org/dr.math/
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