Categories Fractions Number & Operations -- Fractions Subtracting Fractions Post author By mpershan Post date April 29, 2013 4 Comments on Subtracting Fractions I’ve been reading some constructivist stuff lately, so… What resources does this student have for refining their understanding of fractions? (Thanks for the submission, Dionn!) Share this:EmailPrint ← Shall we close up shop? → Money and Decimals 4 replies on “Subtracting Fractions” First, I’d encourage the student to learn with fractions (proper, then improper) before working with mixed numbers again — the mixed number may be what is causing them to “subtract all the numbers the same way”. Converting mixed numbers to improper fractions may be temporarily necessary. Second, a sense of units is needed for the student to understand they can’t add or subtract unlike denominators — they are, however, able to correctly work problems when there is a like denominator (#1, #3, #6 was a near miss). Student doesn’t seem to know that 0/3 = 0; once they learn this the idea can be brought to bear on problems like #12. Student may also have some issues with positive and negative numbers, given the “always positive” result of their subtractions, but it could be an artifact of their fraction understanding gap. I don’t know any resources I would recommend, except to say I think the selection of problems by “Math-Drills.com” is highly suspect. There is no difficulty curve — #2 and #5 are ridiculous compared to the rest of #1-7 (and are the first two examples where the second fraction is larger), and #9 is almost as ugly. #3 is a very poor selection. Also, placing #5 to the right of #1 with #2 below #1 makes me … unwell. That might be the biggest mistake of all here… I recommend Do the Math, by Marilyn Burns, and K-5 Math Teaching Resources (online). Both resources promote the use of models to solve and understand addition and subtraction of fractions. I notice that someone did draw a model on the bottom left corner of the drill sheet. At this stage in understanding, this student should be using a model every time s/he operates on fractions. I like how the student drew a representation on the bottom of the page. I am curious to see how they used it. I wonder how they visualize what is happening. Andy: I’m pretty sure that representation was drawn by someone else, perhaps the teacher; you can tell by the completely different “4” used. Comments are closed.