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Math Help - Grade 8 scientific notation

  1. #1
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    Grade 8 scientific notation

    I have a sum

    (this was all marked last week)

    the sum is 32.4 billion and it says change to scientific notation.
    The teacher says it is 3.24 x 10 to the power of 13.
    Not 14.

    She also says, that 17.52 in scientific notation is 1.752x 10
    because we want it to move by 1 decimal place, so why doesn't the same rule apply for the first sum? Why can't we go 3.24x 10?



    Also, there was a sum I saw on the net.

    93,000,000 to scientific notation

    It says the answer is

    9.3x 10 to the power of 7
    So why can't we have 3.24x 10 to the power of 14 for the 1st sum?

    Please explain, i'm so confused and we have a test tomorrow.

    Oh and also, please don't explain too scientifically because I don't really understand wen it is explained in a very complicated way.



    Thanks!
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  2. #2
    MHF Contributor Unknown008's Avatar
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    1. You have billion following the number, meaning there are 12 more zeroes you need to add.

    32.4 \times 10^{12}

    Now, in scientific notation, you 'want it to move by 1 decimal place' to the left, and hence, you have

    3.24 \times 10 \times 10^{12}

    Which gives 3.24 \times 10^{13}

    2. It's basically 93 with 6 zeroes, or, 93\times 10^6

    You want it into scientific notation, and hence, it becomes 9.3\times 10 \times 10^6 = 9.3 \times 10^7
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  3. #3
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    Quote Originally Posted by Unknown008 View Post
    1. You have billion following the number, meaning there are 12 more zeroes you need to add.

    32.4 \times 10^{12}

    Now, in scientific notation, you 'want it to move by 1 decimal place' to the left, and hence, you have

    3.24 \times 10 \times 10^{12}

    Which gives 3.24 \times 10^{13}

    2. It's basically 93 with 6 zeroes, or, 93\times 10^6

    You want it into scientific notation, and hence, it becomes 9.3\times 10 \times 10^6 = 9.3 \times 10^7

    So how come in the 1st one we don't count the 2 but in the 2nd one we count the 9?
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  4. #4
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    What I mean is, why isn't it 3.24x 10 to the power of 14. Why is it 13?

    when you write 32.4 billion, is it 32.400.000.000.000

    or 32.4000.000.000.000
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  5. #5
    MHF Contributor Unknown008's Avatar
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    32.4 billion is 32 400 000 000 000

    Sorry, in my post above, when I said 12 zeroes, one of them is replaced by the decimal 4, leaving actually 11 zeroes.

    Why power 13? It's because you have moved 13 places from the 'unit' to the left.

    Example:
    350 000 is written as 3.5\times 10^5
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  6. #6
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    Quote Originally Posted by Unknown008 View Post
    32.4 billion is 32 400 000 000 000

    Sorry, in my post above, when I said 12 zeroes, one of them is replaced by the decimal 4, leaving actually 11 zeroes.

    Why power 13? It's because you have moved 13 places from the 'unit' to the left.

    Example:
    350 000 is written as 3.5\times 10^5

    Thank you! Now I understand!!!
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  7. #7
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    Hello out there,
    I suggest that you look up the definition of million and billion.



    bjh
    Last edited by bjhopper; February 14th 2011 at 06:21 PM. Reason: word missing
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