Two Ways to Change Percents to FractionsDate: 02/21/98 at 08:36:46 From: Tiffany Subject: Percents to fractions It is easy until I get to a problem like 10 1/4% and I can't change it into a fraction. Please send me info. Date: 02/23/98 at 11:08:01 From: Doctor Schwenoha Subject: Re: Percents to fractions There are several approaches to deal with this problem. I think it's important for my students to know two of them. The first is probably the easiest in this case. Change the 1/4 to decimal form so that you get 10.25% and now just follow your rules for changing from percent to fraction. The percent sign can be broken down into two parts: per means divided by and cent means 100. Replacing the % sign with this information gives us 10.25/100. Generally we don't like having decimals mixed into fractions (it is not considered "simplest form") so we could multiply this fraction by 100/100 to eliminate the decimal and end up with 1025/10000. We still need to reduce this fraction to be in simplest form and we can divide both the top and the bottom by 25 to get 41/400. 10.25 100 1025 ----- x --- = ----- 100 100 10000 1025 25 41 ----- / -- = --- 10000 25 400 The other method I would want my students to know how to do is to go straight to the definition of the percent sign we just looked at, and make a complex fraction which needs to be simplified. Do you know how to make a whole number into fraction form (just put a fraction bar and a 1 under it)? Do you know how to divide by fractions (multiply by the reciprocal of the divisor)? Here's what it looks like: 41 -- 10 1/4 4 41 1 41 ------ = ----- = -- x --- = --- 100 100 4 100 400 --- 1 We get the same answer either way. I think it's important to know both methods so that we can choose the method that works best for the problem we encounter. I prefer the fraction method (2nd one we looked at) because I think it builds ability in working with any numbers in fraction form. -Doctor Schwenoha, The Math Forum Check out our web site http://mathforum.org/dr.math/ |
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