Q&A #421

Teaching fraction addition

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From: Gail (for Teacher2Teacher Service)
Date: Jul 16, 1998 at 00:32:38
Subject: Re: Teaching fraction addition

Have you ever had students make fractions strips, and then use them to
compare fractional amounts?  In case you haven't here is a quick set of
directions. (You could also buy these materials, but if a child makes them,
that is part of the learning.)

Cut a set of strips that are all the same size.  You can do that by using
lined paper and cutting them so that the lines are running vertically through
the strips ( up and down).  If you make each strip 24 lines long, that will
make some of the folding easier, too.

Now, label the first strip "one whole".  It will be worth one.  Take another
strip, fold it into two equal pieces, and label each one "one half"  (you can
also use the fraction 1/2, to help your students link the word and the
symbol).  Take another strip, and fold it into four equal pieces (to be
labeled fourths).  There is more than one way to do these folds.  To make it
easier to compare them later, making the folds vertically, so the segments
are all in line, is best.  It is a good idea to let your students see how
many different ways they can make these folds to create "equal" pieces,

Continue to make all the fraction pieces from halves to twelfths.  Some
will be more difficult to make than others.  Working through the activity
will help your students see the relationships between the fractions though.
Resist the temptation to do it for them so the materials look neat...

When you are done, you can use these strips to compare fractions to see how
many of one strip make the same sized piece as another strip.  You can also
compare to see which pieces are larger, or smaller than other pieces, for
example, 12 is smaller than 5/8 and 8/12.

Finally, you can use them to add and subtract fractions.  Suppose you want to
add three fourths and one half.  You find the one half strip, and the fourths
strip.  Lay them side by side to notice that one half is the same as two
fourths.  Now lay them one after the other, like a long train.  You have the
half, which is the same as two fourths, and the three fourths.  That is five
fourths all together.  It is longer that the one whole strip, so it must be
worth more than one.   you can compare to find out how much longer than one
it is.

If the fraction were 4 sixths and 3 fourths, you could still add them.  Put
them like a train, and note the length.  Find a strip that compares with both
the sixths and the fourths ( twelfths work)  Change the names of the two
fractions into twelfth, by comparing.  Then figure out by substituting how
many twelfths you have...

 -Gail, for the Teacher2Teacher service

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