WEBVTT

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>> I'm Keith Phelps.

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I teach fourth grade at Spalding
Elementary School of Math

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and Technology in Meridian
School District in Boise, Idaho.

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Today we did a lesson on
decomposing fractions.

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We started with one and
a half and we're looking

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at different ways to
make one and a half.

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I really try to think
about the numbers I'm going

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to use beforehand.

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I like to try the problems
out myself before I do them

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to make sure it's a good fit.

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One and a half seemed like
a good number to use today

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because there's so many
different ways that you can come

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up with one and a half,

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especially using the
pieces that we had.

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It let to some great discussion
about wholes and halves

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that we're going to
come back to later.

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>> Phelps (to class): My son's
birthday's coming up, Henry,

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and I want to make
him a birthday cake

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but I have a little problem.

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The recipe for the
birthday cake calls for one

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and a half cups of flour.

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Well, I lost my one
cup and my half a cup.

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So fortunately, I have lots

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of different kinds
of measuring cups.

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So I need your help today
to figure out different ways

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that I can still measure out
one and a half cups of flour

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so I can make this
cake for my son.

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These bars are going to
represent my measuring cups.

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I have a fourth cup
and I have a third cup.

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I have a sixth cup, a fifth cup.

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I have twelfths.

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Really some odd sizes;

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you usually can't
find these in a store.

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An eighth of a cup
and I have tenths.

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Think for a second, what are
some different ways you can come

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up with one and a half cups.

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So go ahead and just talk
amongst yourselves and think

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of any ways right off
the top of your heads.

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Let's hear what some
of your ideas were.

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Kayden?

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>> Kayden: You could
do some twelfths.

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>> Phelps: Some twelfths.

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>> Kayden: Or any one.

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>> Phelps: Okay.

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All right, so do you know how
many twelfths I would need?

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>> Kayden: Maybe about six.

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>> Phelps: About six twelfths.

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>> Kayden: Maybe a little more.

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>> Phelps: Maybe
a little bit more.

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Okay. Hannah, what do you think?

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>> Hannah: You need twelve
and six cups and six more.

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You need twelve plus six.

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>> Phelps: Twelve plus six.

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And why is that, Hannah?

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>> Hannah: Because there
will be twelve in one whole

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and six to make the half.

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>> Phelps: Oh, okay.

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Does that sound reasonable,
Kayden?

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>> Kayden: Uh-uh.

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>> Phelps: Okay.

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So if I drew a picture here.

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So if I'm going to use twelfths,

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Hannah said I need
twelve twelfths

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to make the whole, the one cup.

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Let's see if I can divide
this up into twelfths.

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That's going to be a lot of
scoops using my twelfths.

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That's my smallest one.

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I'm going to have to do
a lot of scoops there.

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Okay and then how many,
class all together,

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how many did I need here?

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>> Class: Six.

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>> Phelps: Six, okay.

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I'm going to have you use the
blocks, and I want you to come

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up with different ways,
this is just one way,

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I want you to build
it with the blocks.

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After you've built it, then I
would like you to draw a picture

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of it like I've done,
drawn a picture here,

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and then I want you to do
a number sentence for this.

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So you're going to build it.

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After you build it, what are
we going to do, everybody?

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>> Class: Draw.

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>> Phelps: Draw it.

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And then the last step is?

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>> Class: Write a sentence.

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>> Phelps: The number sentence.

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>> Phelps: It's important
for students to be able

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to decompose fractions, be able
to see equivalent fractions,

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landmark fractions,
halves and wholes are key.

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Just building that foundation
is really important later

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on for addition, subtraction,
operations with fractions.

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I try to use a lot of
different representations;

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a lot of different
manipulatives, even bringing

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in real-life examples of
fractions like measuring cups.

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For this particular
lesson it worked better

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to use the premade
fraction pieces.

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>> Phelps (to class): I
had a few people come up

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and draw their pictures
up on the board,

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so I want to take a
second and have you come up

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and explain your pictures to us

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and see what you
found out, okay?

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This first one was Hailey.

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Hailey, will you come up and
explain what you have here

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and what you found out.

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>> Hailey: I knew that about
six sixths would equal one whole

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and three sixths
will equal half.

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So I did about nine sixths
to make one and a half cups.

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>> Phelps: So I'd to have to
use a sixth cup nine times

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to get one and a half cups.

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Let's see what happens
when we use fifths.

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>> Student: So it
does work with five

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because five-fifths equal
a whole except for you need

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to know what half of five is,
but since it's odd you have

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to have a two and a half.

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But there's no two and a
half, so you can't do it.

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>> Phelps: So for
the whole it works

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>> Student: Mm-hmm.

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>> Phelps: But for the
half, fifths don't work.

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>> Student: Yeah.

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>> Phelps: So I would use
five-fifths for the whole

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and then somewhere
between-you weren't sure

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if it was two-fifths or
three-fifths that would go here.

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>> Student: Yeah.

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>> Phelps: All right.

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Does anybody know
what it would be?

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Jayden?

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>> Jayden: You would have
five-fifths to make a whole

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and then you would have two more
fifths 'cause three-fifths won't

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go into half 'cause that's
more than half of five.

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And then you'd have to
have a half of a fifth,

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and then you'd have to
have seven and a half

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to make one and a half.

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>> Phelps: Okay.

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Good. Does anybody know
what half a fifth is?

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All right, which block is
half of fifth everybody?

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>> Class: One-tenth.

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>> Phelps: One-tenth, okay.

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Cool. One-tenth, so I would
need five plus two and a half.

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So that would be seven
and a half-fifths

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or seven-fifths and one-tenth.