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    T to the power 3= mn/m-n

    M=4x10 to the power 12
    N=3x10 to the power 9

    Work out T.

    Eh I multiplied m and n together (to get MN) and got 12x10 to the power 21 (I know you can't have numbers above 12 in standard form but I have no idea whether what I'm doing is correct).

    Then I did m-n and got 1x10 to the power 3.

    Did the division sum= 12x10 to the power 21 divided by 1x10 to the power 3 and got 12x10 to the power 18=1.2x10 to the power 19.

    T to the power 3= 1.2x10 to the power 19.

    'Cube rooted' it and the answer I got for T was 2289428.485.

    It wants the answer in standard form to 3 significant figures= 2.29x10 the power 6.

    Is this completely wrong or? Probably just over complicated a really simple question but help would be appreciated
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    (Original post by idfk_)
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    Your first step (m x n) is correct. However, 4\times 10^{12} - 3\times 10^9 is not 1\times 10^3. Adding and subtracting gets a bit more complicated if the tens are to different powers (you do not subtract the exponents if you're just doing subtraction) so if you're not using a calculator, you need to manually put them to the same power. 3\times 10^9 = 0.003\times 10^12 so m - n = 4\times 10^{12} - 0.003\times 10^{12} = 3.997 \times 10^{12}.
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    (Original post by Plagioclase)
    Your first step (m x n) is correct. However, 4\times 10^{12} - 3\times 10^9 is not 1\times 10^3. Adding and subtracting gets a bit more complicated if the tens are to different powers (you do not subtract the exponents if you're just doing subtraction) so if you're not using a calculator, you need to manually put them to the same power. 3\times 10^9 = 0.003\times 10^12 so m - n = 4\times 10^{12} - 0.003\times 10^{12} = 3.997 \times 10^{12}.
    Thankyou!!

    So, would I go about it the same way when I do the division and then cube root the answer to get to T?
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    (Original post by idfk_)
    Thankyou!!

    So, would I go about it the same way when I do the division and then cube root the answer to get to T?
    So you now know what mn and m-n are ( 12 \times 10^{21} = 1.2 \times 10^{22} and  3.997\times 10^{12} respectively) so yes, you just do a simple division. You will probably want to do this on your calculator though, unless you're particularly keen on working out what \frac{1.2}{3.997} is by hand!
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    (Original post by Plagioclase)
    So you now know what mn and m-n are ( 12 \times 10^{21} = 1.2 \times 10^{22} and  3.997\times 10^{12} respectively) so yes, you just do a simple division. You will probably want to do this on your calculator though, unless you're particularly keen on working out what \frac{1.2}{3.997} is by hand!
    Calculator it is.

    From that I get the answer 3002251689. Cube root it to get T=1442.610313

    Which is equal to 1.44x10 to the power 3?
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    (Original post by idfk_)
    Calculator it is.

    From that I get the answer 3002251689. Cube root it to get T=1442.610313

    Which is equal to 1.44x10 to the power 3?
    Yep, that's what I've got! :yep:
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    (Original post by Plagioclase)
    Yep, that's what I've got! :yep:
    Again, thanks a lot! Wouldn't have got to that myself
 
 
 
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