## Multiplying Fractions Word Problem

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A recipe for banana oat muffins
calls for 3/4 of a cup
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of old-fashioned oats.
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You are making 1/2
of the recipe.
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How much oats should you use?
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So if the whole recipe requires
3/4 of a cup and
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you're making half of
the recipe, you want
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half of 3/4, right?
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You want half of the number of
old-fashioned oats as the
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whole recipe.
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So you want 1/2 of 3/4.
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So you just multiply 1/2 times
3/4, and this is equal to--
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you multiply the numerators.
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1 times 3 is 3.
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2 times 4 is 8.
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And we're done!
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You need 3/8 of a cup of
old-fashioned oats.
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And let's visualize that a
little bit, just so it makes a
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little bit more sense.
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Let me draw what 3/4 looks like,
or essentially how much
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oats you would need in a normal
situation, or if you're
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doing the whole recipe.
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So let me draw.
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Let's say this represents a
whole cup, and if we put it
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into fourths-- let me divide
it a little bit better.
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So if we put it into fourths,
3/4 would represent three of
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these, so it would represent
one, two, three.
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It would represent
that many oats.
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Now, you want half
of this, right?
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Because you're going to make
half of the recipe.
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So we can just split
this in half.
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Let me do this with
a new color.
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So you would normally use this
orange amount of oats, but
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we're going to do half the
recipe, so you'd want
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half as many oats.
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So you would want
this many oats.
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what that is
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relative to a whole cup.
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Well, one way we can do it is
to turn each of these four
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buckets, or these four pieces,
or these four sections of a
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cup into eight sections
of a cup.
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Let's see what happens
when we do that.
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So we're essentially turning
each piece, each fourth, into
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two pieces.
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So let's divide each
of them into two.
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So this is the first piece.
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We're going to divide it into
two right there, so now it is
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two pieces.
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And then this is the second
piece right here.
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We divide it into one piece
and then two pieces.
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This is the third piece, so
we divide it into one, two
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pieces, and this is the fourth
piece, or the fourth section,
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and we divide it into
two sections.
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Now, what is this as a fraction
of the whole?
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Well, we have eight
pieces now, right?
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One, two, three, four, five,
six, seven, eight, because we
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turned each of the four, we
split them again into eight,
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so we have 8 as the denominator,
and we took half
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of the 3/4, right?
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Remember, 3/4 was in orange.
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Let me make this very
clear because this
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drawing can get confusing.
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This was 3/4 right there.
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So that is 3/4.
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This area in this purple color
is 1/2 of the 3/4.
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in terms of the eights.
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How many of these sections
of eight is it?
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Well, you have one section of
eight here, two sections of
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eight there, three sections
of eight, so it is 3/8.
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So hopefully that makes some
sense or gives you a more
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tangible feel for what
it means when
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you take 1/2 of 3/4.
Title:
Multiplying Fractions Word Problem
Description:

U02_L2_T1_we4 Multiplying Fractions Word Problem

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Video Language:
English
Duration:
03:39
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