Learner Posted February 1, 2011 Share Posted February 1, 2011 I need help to teach fractions to my 4th grader, arranging them smallest to largest, when all denominators are different. I thought of Least common factor, but he doesnt know how to find that yet, converting to decimals will take forever if there are 5-7 fractions to be compared. Example is: 3/12, 4/10, 2/17, 3/ 19, 3/5, 1/11 Please advice. Quote Link to comment Share on other sites More sharing options...
cschnee Posted February 1, 2011 Share Posted February 1, 2011 The books, Lessons for Introducing Fractions and Lessons for Extending Fractions both by Marilyn Burns are excellent for learning about fractions. A lot of the lessons look at making 1/2 a bench mark and seeing how other fractions differ from 1/2. Are they bigger or smaller...by how much? Quote Link to comment Share on other sites More sharing options...
Learner Posted February 1, 2011 Author Share Posted February 1, 2011 Any further help???:001_huh: Quote Link to comment Share on other sites More sharing options...
Ray Posted February 1, 2011 Share Posted February 1, 2011 Equivalent fractions, cross product, and number line. All take time, the first two are computational methods with the third being good for developing number sense. Quote Link to comment Share on other sites More sharing options...
Crimson Wife Posted February 1, 2011 Share Posted February 1, 2011 I really like the Learning Resources Rainbow Fraction Tiles set. It won't help with the odd-ball denominators (like seventeenths) but it will really help the child visualize the common ones (halves, thirds, fourths, fifths, sixths, eighths, tenths, and twelfths). I also highly recommend the MM single-topic "blue" worktexts Fractions 1 and Fractions 2. Quote Link to comment Share on other sites More sharing options...
Paintedlady Posted February 1, 2011 Share Posted February 1, 2011 Maybe back up just a bit and teach him how to find the common denominators of only 2 fractions at first, and once he's solid with that, slowly move him into finding the common denominators of several fractions. My new tactic for tackling fractions is to have my kids go through the Key To Fractions books first before continuing into their regular math curricula (we use MUS). I like that the Key To series is a very visual and gentle introduction into fractions without overwhelming them. When they get back to their regular curricula it seems more like a review but with some added depth. Hope that makes sense and is helpful to you! :001_smile: Quote Link to comment Share on other sites More sharing options...
Learner Posted February 1, 2011 Author Share Posted February 1, 2011 Equivalent fractions, cross product, and number line. All take time, the first two are computational methods with the third being good for developing number sense. How can I teach with number Line...not sure about this one. I wil also look into MM blue series for fractions.. Thanks for your help! Quote Link to comment Share on other sites More sharing options...
Ray Posted February 1, 2011 Share Posted February 1, 2011 How can I teach with number Line...not sure about this one. Do you have a ruler or tape measure around. http://mathforum.org/library/drmath/view/58167.html And how about the kitchen those Pyrex Measuring cups lay out a 'number line'vertical style. Naulgene canteens also have useful measurement marking + fun of interactive watery mess making. The fractional puzzle that crimson mom linked is another form of 'number line', just with more parts than marks. A number line is a powerful tool for internalizing and making sense of things like 3/5 > 3/19. Quote Link to comment Share on other sites More sharing options...
MerryAtHope Posted February 2, 2011 Share Posted February 2, 2011 Are you using a book--how does the book expect him to do it? Here's how I would do it: First, see which numbers are more than 1/2 and which are less. Right away I can divide them into 2 groups this way: 3/5 is more, the rest are less. Also right away I can see that 4/10 is very nearly 1/2, so that's the next largest. That leaves me with these 4: 3/12, 2/17, 3/19, 1/11 If he knows that 3/12 is the same as 1/4, he can see that that's the next largest--the rest are smaller than 1/4. The next thing I would do is compare 1/11 to all of the others, because it's easy to double and make it 2/22. Then I can easily see that it is the smallest fraction--the smaller the denominator, the larger each individual piece is--so 2/17, and 3/19 are all going to be larger than 1/11. That leaves us with 2/17 and 3/19, which are pretty easy to compare, and decide that 3/19 is bigger. So we'd have: 1/11, 2/17, 3/19, 3/12, 4/10, 3/5 Merry :-) Quote Link to comment Share on other sites More sharing options...
buddhabelly Posted February 2, 2011 Share Posted February 2, 2011 Perhaps you have already answered this, but why now in 4th grade? My son is in sixth grade at a good school, and they are just now doing this in 6th grade. I highly recommend Life of Fred "Fractions and Decimals" in general, which my son completed in 5th grade, but the task you are describing is not simple and is not likely to be retained if it's not presented in a logical sequence in your curriculum. But, of course, YMMV. Julie Quote Link to comment Share on other sites More sharing options...
Mommybostic Posted February 2, 2011 Share Posted February 2, 2011 I like Life of Fred: Fractions. I would say knowing how to find the least common denominator (or least common factor) is necessary, but even that method would be VERY difficult with this problem. I think using a ruler and drawing six bars would work. Divide each one evenly into however many parts (12, 10, etc.), then color in the right fraction and compare them that way. I don't know, maybe that's not the best method, but it's all I could think of. Quote Link to comment Share on other sites More sharing options...
Jay3fer Posted February 2, 2011 Share Posted February 2, 2011 If I may suggest something a little different: JUMP Math offers an introduction to fractions that: - assumes no prior skills beyond multiplying by 2s, 4s and 5s (I believe - maybe 3s?) - begins at the ground floor - quickly moves kids up, through VERY simple steps, to full fluency in fraction operations This mini-curriculum can be found with tons of other information at this site - everything is downloadable as a PDF, as far as I can tell. The author, John Mighton (who himself came to math a bit late in life), has also written a helpful book: The Myth of Ability: Nurturing Mathematical Talent in Every Child. I blogged about this when I read it - just a couple of weeks ago. Hope this is helpful... seriously, check it out. It's FREE and easy to work through. Quote Link to comment Share on other sites More sharing options...
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