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September 23rd, 2012, 06:28 AM  #1 
Senior Member Joined: Sep 2009 Posts: 251 Thanks: 0  Divide a 7/3 bar into 3/4
Hi. I can't find the right place for these questions. I think there is not a "just right" forum on here. Anyway, this question is for a "Teaching of Mathematics" course my friend is in. I don't get the questions. I mean, what are they asking? What do they want her to do? 1b. Suppose that the bar in following represents 7/3. Create a bar that is equivalent to 3/4. (Then there is a picture of a horizontal bar.) 3. This question has one bar which is divided into 7 equal parts and another bar which is divided into 5 equal parts. The bars are horizontal, leftaligned, and equal length. The question is: Use a bar model to determine which one is bigger, 4/7 or 3/5, and explain how much one is bigger than the other. You must not calculate to find the solution and your explanation must be thorough. (Emphasis is mine.) I enclosed a couple of pictures to enhance my outstanding (cough, cough ) descriptions. Thanks for helpin'. J. [attachment=2:kfi8yrwz]CaptureA.PNG[/attachment:kfi8yrwz] [attachment=1:kfi8yrwz]CaptureB.PNG[/attachment:kfi8yrwz] [attachment=0:kfi8yrwz]Capture3.PNG[/attachment:kfi8yrwz] 
September 23rd, 2012, 07:16 AM  #2 
Senior Member Joined: Jul 2010 From: St. Augustine, FL., U.S.A.'s oldest city Posts: 12,211 Thanks: 521 Math Focus: Calculus/ODEs  Re: Divide a 7/3 bar into 3/4
Here's how I would do the first one: [attachment=0:jdao3t93]bar1.jpg[/attachment:jdao3t93] First, divide the bar into 5 equal segments, each segment representing 1/4 unit. Second, divide each segment into 5 equal subsegments since the denominator of 3/5 is 5, each subsegment representing 1/20 unit. Since 3/5 = 12/20, remove 12 subsegments for a bar 3/5 units in length. This suggests . For the second one, divide the bar into 7 equal segments, each segment representing 1/3 unit. Since the denominator of 3/4 is 4, divide each segment into 4 subsegments, each representing 1/12 unit. Since 3/4 = 9/12, remove 9 subsegments for a bar 3/4 unit in length. For the third one: In the top bar, divide each segment into 5 subsegments, each subsegment representing 1/35 unit. In the bottom bar, divide each segment into 7 subsegments, each subsegment representing 1/35 unit. Now, count how many subsegments are between the bold lines in each bar. This number is n. Then we know 4/7 + n/35 = 3/5. 

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3 or 4, 7 or 3, bar, divide 
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