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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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    Now, let's think about
    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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    But let's think about it
    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

English subtitles

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