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Scientific Notation Examples

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    It always helps me to see a lot
    of examples of something so I
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    figured it wouldn't hurt to
    do more scientific
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    notation examples.
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    So I'm just going to write a
    bunch of numbers and then write
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    them in scientific notation.
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    And hopefully this'll cover
    almost every case you'll ever
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    see and then at the end of this
    video, we'll actually do some
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    computation with them to just
    make sure that we can
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    do computation with
    scientific notation.
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    Let me just write down
    a bunch of numbers.
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    0.00852.
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    That's my first number.
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    My second number
    is 7012000000000.
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    I'm just arbitrarily
    stopping the zeroes.
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    The next number is 0.0000000
    I'll just draw a couple more.
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    If I keep saying 0, you
    might find that annoying.
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    500 The next number --
    right here, there's a
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    decimal right there.
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    The next number I'm going
    to do is the number 723.
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    The next number I'll do -- I'm
    having a lot of 7's here.
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    Let's do 0.6.
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    And then let's just do one more
    just for, just to make sure
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    we've covered all of our bases.
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    Let's say we do 823 and then
    let's throw some -- an
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    arbitrary number of 0's there.
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    So this first one, right here,
    what we do if we want to write
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    in scientific notation, we want
    to figure out the largest
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    exponent of 10 that
    fits into it.
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    So we go to its first
    non-zero term, which
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    is that right there.
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    We count how many positions to
    the right of the decimal point
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    we have including that term.
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    So we have one, two, three.
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    So it's going to
    be equal to this.
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    So it's going to be equal
    to 8 -- that's that guy
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    right there -- 0.52.
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    So everything after that
    first term is going to
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    be behind the decimal.
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    So 0.52 times 10 to the
    number of terms we have.
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    One, two, three.
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    10 to the minus 3.
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    Another way to think of it:
    this is a little bit more.
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    This is like 8 1/2
    thousands, right?
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    Each of these is thousands.
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    We have 8 1/2 of them.
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    Let's do this one.
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    Let's see how many 0's we have.
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    We have 3, 6, 9, 12.
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    So we want to do -- again,
    we start with our largest
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    term that we have.
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    Our largest non-zero term.
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    In this case, it's going
    to be the term all
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    the way to the left.
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    That's our 7.
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    So it's going to be 7.012.
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    It's going to be equal to
    7.012 times 10 to the what?
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    Well it's going to be times 10
    to the 1 with this many 0's.
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    So how many things?
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    We had a 1 here.
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    Then we had 1, 2, 3, 4, 5,
    6, 7, 8, 9, 10, 11, 12 0's.
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    I want to be very clear.
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    You're not just
    counting the 0's.
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    You're counting everything
    after this first
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    term right there.
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    So it would be equivalent
    to a 1 followed by 12 0's.
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    So it's times 10
    to the twelfth.
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    Just like that.
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    Not too difficult.
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    Let's do this one right here.
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    So we go behind our
    decimal point.
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    We find the first
    non-zero number.
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    That's our 5.
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    It's going to be equal to 5.
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    There's nothing to the right of
    it, so it's 5.00 if we wanted
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    to add some precision to it.
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    But it's 5 times and then how
    many numbers to the right, or
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    behind to the right of the
    decimal will do we have?
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    We have 1, 2, 3, 4, 5, 6, 7,
    8, 9, 10, 11, 12, 13, and we
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    have to include this one, 14.
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    5 times 10 to the
    minus 14th power.
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    Now this number, it might be a
    little overkill to write this
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    in scientific notation, but it
    never hurts to get
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    the practice.
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    So what's the largest 10
    that goes into this?
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    Well, 100 will go into this.
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    And you could figure out 100 or
    10 squared by saying, "OK, this
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    is our largest term." And then
    we have two 0's behind it
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    because we can say 100
    will go into 723.
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    So this is going to be equal to
    7.23 times, we could say times
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    100, but we want to stay in
    scientific notation, so I'll
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    write times 10 squared.
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    Now we have this
    character right here.
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    What's our first non-zero term?
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    It's that one right there, so
    it's going to be 6 times and
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    then how many terms do we have
    to the right of the decimal?
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    We have only one.
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    So times 10 to the minus 1.
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    That makes a lot of sense
    because that's essentially
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    equal to 6 divided by 10
    because 10 to the minus
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    1 is 1/10 which is 0.6.
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    One more.
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    Let me throw some commas
    here just to make this a
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    little easier to look at.
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    So let's take our largest
    value right there.
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    We have our 8.
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    This is going to be 8.23 -- we
    don't have to add the other
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    stuff because everything else
    is a 0 -- times 10 to the --
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    we just count how many
    terms are after the 8.
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    So we have 1, 2, 3, 4,
    5, 6, 7, 8, 9, 10.
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    8.23 times 10 to the 10.
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    I think you get the idea now.
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    It's pretty straightforward.
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    And more than just being able
    to calculate this, which is a
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    good skill by itself, I want
    you to understand why
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    this is the case.
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    Hopefully that last
    video explained it.
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    And if it doesn't, just
    multiply this out.
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    Literally multiply 8.23
    times 10 to the 10 and
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    you will get this number.
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    Maybe you could try it
    with something smaller
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    than 10 to the 10.
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    Maybe 10 to the fifth.
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    And well, you'll get a
    different number but
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    you'll end up with five
    digits after the 8.
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    But anyway, let me do a couple
    more computation examples.
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    Let's say we had the numbers
    -- let me just make something
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    really small -- 0.0000064.
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    Let me make a large number.
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    Let's say I have that number
    and I want to multiply it.
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    I want to multiply it by --
    let's say I have a really large
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    number -- 3 2 -- I'm just going
    to throw a bunch of 0's here.
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    I don't know when
    I'm going to stop.
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    Let's say I stop there.
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    So this one, you
    can multiply out.
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    But it's a little difficult.
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    But let's put it into
    scientific notation.
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    One, it'll be easier to
    represent these numbers and
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    then hopefully you'll see that
    the multiplication actually
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    gets simplified as well.
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    So this top guy right here,
    how can we write him in
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    scientific notation?
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    It would be 6.4 times
    10 to the what?
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    1, 2, 3, 4, 5, 6.
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    I have to include the 6.
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    So times 10 to the minus 6.
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    And what can this
    one be written as?
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    This one is going to be 3.2.
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    And then you count how many
    digits are after the 3.
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    1, 2, 3, 4, 5, 6,
    7, 8, 9, 10, 11.
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    So 3.2 times 10 to the 11th.
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    So if we multiply these two
    things, this is equivalent to 6
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    -- let me do it in a different
    color -- 6.4 times 10 to
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    the minus 6 times 3.2
    times 10 to the 11th.
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    Which we saw in the last video
    is equivalent to 6.4 times 3.2.
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    I'm just changing the order
    of our multiplication.
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    Times 10 to the minus 6
    times 10 to the 11th power.
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    And now what will
    this be equal to?
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    Well, to do this, I don't
    want to use a calculator.
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    So let's just calculate it.
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    So 6.4 times 3.2.
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    Let's ignore the
    decimals for a second.
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    We'll worry about
    that at the end.
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    So 2 times 4 is 8,
    2 times 6 is 12.
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    Nowhere to carry the
    1, so it's just 128.
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    Put a 0 down there.
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    3 times 4 is 12, carry the 1.
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    3 times 6 is 18.
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    You've got a 1
    there, so it's 192.
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    Right?
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    Yeah.
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    192.
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    You had them up and you
    get 8, 4, 1 plus 9 is 10.
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    Carry the 1.
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    You get 2.
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    Now, we just have to
    count the numbers behind
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    the decimal point.
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    We have one number there, we
    have another number there.
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    We have two numbers behind
    the decimal point,
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    so you count 1, 2.
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    So 6.4 times 3.2 is equal to
    20.48 times 10 to the -- we
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    have the same base here, so we
    can just add the exponents.
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    So what's minus 6 plus 11?
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    So that's 10 to the
    fifth power, right?
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    Right.
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    Minus 6 and 11.
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    10 to the fifth power.
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    And so the next question,
    you might say, "I'm done.
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    I've done the computation."
    And you have.
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    And this is a valid answer.
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    But the next question is is
    this in scientific notation?
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    And if you wanted to be a real
    stickler about it, it's not in
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    scientific notation because we
    have something here that could
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    maybe be simplified
    a little bit.
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    We could write this --
    let me do it this way.
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    Let me divide this by 10.
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    So any number we can
    multiply and divide by 10.
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    So we could rewrite
    it this way.
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    We could write 1/10 on this
    side and then we can multiply
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    times 10 on that side, right?
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    That shouldn't
    change the number.
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    You divide by 10 and
    multiply it by 10.
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    That's just like multiplying
    by 1 or dividing by 1.
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    So if you divide this side
    by 10, you get 2.048.
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    You multiply that side by
    10 and you get times 10 to
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    the -- times 10 is just
    times 10 to the first.
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    You can just add the exponents.
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    Times 10 to the sixth.
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    And now, if you're a stickler
    about it, this is good
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    scientific notation
    right there.
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    Now, I've done a lot
    of multiplication.
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    Let's do some division.
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    Let's divide this
    guy by that guy.
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    So if we have 3.2 times 10 to
    the eleventh power divided by
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    6.4 times 10 to the minus
    six, what is this equal to?
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    Well, this is equal
    to 3.2 over 6.4.
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    We can just separate them out
    because it's associative.
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    So, it's this times 10
    to the 11th over 10 to
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    the minus six, right?
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    If you multiply these
    two things, you'll
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    get that right there.
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    So 3.2 over 6.4.
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    This is just equal
    to 0.5, right?
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    32 is half of 64 or 3.2
    is half of 6.4, so this
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    is 0.5 right there.
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    And what is this?
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    This is 10 to the 11th
    over 10 to the minus 6.
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    So when you have something
    in the denominator, you
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    could write it this way.
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    This is equivalent to 10 to the
    11th over 10 to the minus 6.
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    It's equal to 10 to the
    11th times 10 to the
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    minus 6 to the minus 1.
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    Or this is equal to 10 to the
    11th times 10 to the sixth.
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    And what did I do just there?
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    This is 1 over 10
    to the minus 6.
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    So 1 over something is just
    that something to the
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    negative 1 power.
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    And then I multiplied
    the exponents.
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    You can think of it that way
    and so this would be equal
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    to 10 to the 17th power.
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    Or another way to think about
    it is if you have 1 -- you have
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    the same bases, 10 in this
    case, and you're dividing them,
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    you just take the 1 the
    numerator and you subtract the
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    exponent in the denominator.
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    So it's 11 minus minus
    6, which is 11 plus 6,
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    which is equal to 17.
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    So this division problem
    ended up being equal to
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    0.5 times 10 to the 17th.
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    Which is the correct answer,
    but if you wanted to be a
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    stickler and put it into
    scientific notation, we want
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    something maybe greater
    than 1 right here.
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    So the way we can do
    that, let's multiply
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    it by 10 on this side.
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    And divide by 10 on this
    side or multiply by 1/10.
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    Remember, we're not changing
    the number if you multiply
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    by 10 and divide by 10.
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    We're just doing it to
    different parts of the product.
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    So this side is going to become
    5 -- I'll do it in pink -- 10
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    times 0.5 is 5, times 10 to
    the 17th divided by 10.
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    That's the same thing as
    10 to the 17th times 10
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    to the minus 1, right?
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    That's 10 to the minus 1.
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    So it's equal to 10
    to the 16th power.
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    Which is the answer when
    you divide these two
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    guys right there.
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    So hopefully these examples
    have filled in all of the
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    gaps or the uncertain
    scenarios dealing with
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    scientific notation.
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    If I haven't covered something,
    feel free to write a comment on
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    this video or pop me an e-mail.
Title:
Scientific Notation Examples
Description:

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Video Language:
English
Team:
Khan Academy
Duration:
12:49

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