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# Help w MathsðŸ™ƒ

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1. 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
2. (Original post by idfk_)
X
Your first step (m x n) is correct. However, is not . 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. so .
3. (Original post by Plagioclase)
Your first step (m x n) is correct. However, is not . 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. so .
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?
4. (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 and are ( and 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 is by hand!
5. (Original post by Plagioclase)
So you now know what and are ( and 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 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?
6. (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!
7. (Original post by Plagioclase)
Yep, that's what I've got!
Again, thanks a lot! Wouldn't have got to that myself

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