Demonstrating Equivalent Fractions
Date: 10/25/2000 at 10:24:54 From: Karen Harris Subject: Equivalent fractions My daughter is a 5th grader in a gifted class. She has been given an assignment to teach other children in her class about equivalent fractions. The demonstration must last at least 10 minutes, and she must use visuals. She does not understand the concept well enough, she feels, to explain and demonstrate to others. I am trying to help her with a lesson plan that would be unique and simple so that she can learn as well as teach others her age. I have gone to various sites and am having a difficult time finding something I can explain to her and that she can use.
Date: 10/25/2000 at 13:09:55 From: Doctor Peterson Subject: Re: Equivalent fractions Hi, Karen. One thing to do first is to go to our search page and enter the phrase "equivalent fractions" (don't use the quotes, and check the button for 'that exact phrase'). There your daughter will be able to look through examples of how we have explained the concept to others, which may give a number of different approaches to try - one of which may be just what she needs in order to feel more confident about it. Here's my favorite way. Take a sheet of paper and divide it into some number of columns, and shade some of them in: +---+---+---+ |XXX|XXX| | |XXX|XXX| | |XXX|XXX| | |XXX|XXX| | |XXX|XXX| | |XXX|XXX| | |XXX|XXX| | +---+---+---+ Now make several copies of this, by hand or with a copier. Label the shaded part on the original "2/3" (in my example). Now take one of the copies and draw a line across the middle +---+---+---+ |XXX|XXX| | |XXX|XXX| | |XXX|XXX| | +---+---+---+ |XXX|XXX| | |XXX|XXX| | |XXX|XXX| | +---+---+---+ Suddenly the 2/3 has changed to 4/6! Write "4/6" on the shaded part. You could have fun with this and act like it's a magic trick, making the change behind a scarf. If someone puts the act down, saying nothing really changed, well, that's the whole point. Fractions aren't magic, they're just common sense. Now ask someone in the audience if (s)he can see how to change the thirds (on another sheet) into ninths, or twelfths. After repeating this a few times, you will have a set of equivalent fractions taped to the board: 2/3, 4/6, 6/9, 8/12, and so on. These are all different ways to name the same fraction. Now here comes the real math. Write on the board: 2 2 4 --- x --- = --- 3 2 6 This explains what the first equivalent fraction means: we have twice as many pieces in all (the denominator - which means "namer," since it says that each piece is a "third"); and also twice as many pieces in our fraction (the numerator - which means "numberer," since it tells how many of those pieces we have.) In multiplying both by the same number, we do not change the meaning of the fraction. If there is time, your daughter might like to think up a way to do the same sort of thing, but starting with a fraction that is not in lowest terms, such as 4/6. One way is to color in 4 of 6 columns (probably best done with the paper in landscape position), then cut them all apart and rearrange them from 1 by 6 into a 2 by 3 formation, with the shaded pieces looking the way they do in my picture for 4/6. Proper use of tape can change the fraction to 2/3. The fact that both numerator and denominator can be evenly divided by 2 allows this to be done; you couldn't make such a rearrangement for 5/6, though you could for 3/6. There's a lot to learn by playing like this! - Doctor Peterson, The Math Forum http://mathforum.org/dr.math/
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