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 June 20th, 2013, 10:23 PM #1 Newbie   Joined: May 2012 Posts: 21 Thanks: 0 help me solve this please, I need the steps!! k = 25 (n/100)^(1/2) =4.5k^(0.5)n^(-0.5) anyone can show me the step how to solve for n? I know the answer is n=225, but don't know how to get it. solve for n.
 June 21st, 2013, 12:00 AM #2 Senior Member     Joined: Jul 2010 From: St. Augustine, FL., U.S.A.'s oldest city Posts: 12,168 Thanks: 472 Math Focus: Calculus/ODEs Re: help me solve this please, I need the steps!! We may write the equation as: $\sqrt{\frac{n}{100}}=4.5\sqrt{\frac{k}{n}}$ With $k=25$ we may simplify as follows: $\frac{\sqrt{n}}{10}=4.5\cdot\frac{5}{\sqrt{n}}$ $\sqrt{n^2}=45\cdot5$ Assuming the original radicands are non-negative, we find: $n=225$
 June 21st, 2013, 02:57 AM #3 Math Team     Joined: May 2013 From: The Astral plane Posts: 1,797 Thanks: 715 Math Focus: Wibbly wobbly timey-wimey stuff. Re: help me solve this please, I need the steps!! I missed that last line about the negatives. I can edit my posts now!! -Dan
June 21st, 2013, 07:27 AM   #4
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Re: help me solve this please, I need the steps!!

Quote:
 Originally Posted by topsquark I missed that last line about the negatives. I can edit my posts now!! -Dan
I originally had $n=\pm225$, and then added the line about the radicands being non-negative, but didn't change the solution to just the positive case (which I have fixed now).

 June 21st, 2013, 02:05 PM #5 Newbie   Joined: May 2012 Posts: 21 Thanks: 0 Re: help me solve this please, I need the steps!! Thanks guys, the is really helpful, but I have one more question, the only thing I dont get with the steps is step 1, on the part 4.5k^(0.5)n^(-0.5) become 4.5sqrt(k/n), can someone explain that particular part for me please?
June 21st, 2013, 02:25 PM   #6
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Re: help me solve this please, I need the steps!!

Quote:
 Originally Posted by MarkFL $\frac{\sqrt{n}}{10}=4.5\cdot\frac{5}{\sqrt{n}}$ $\sqrt{n^2}=45\cdot5$ $n=225$

June 21st, 2013, 03:05 PM   #7
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Re: help me solve this please, I need the steps!!

Quote:
Originally Posted by eddybob123

Quote:
 Originally Posted by MarkFL $\frac{\sqrt{n}}{10}=4.5\cdot\frac{5}{\sqrt{n}}$ $\sqrt{n^2}=45\cdot5$ $n=225$
How so? You left out the part in your quote where I stated the assumption about the radicands being non-negative.

June 21st, 2013, 03:07 PM   #8
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Re: help me solve this please, I need the steps!!

Quote:
 Originally Posted by ahereicome Thanks guys, the is really helpful, but I have one more question, the only thing I dont get with the steps is step 1, on the part 4.5k^(0.5)n^(-0.5) become 4.5sqrt(k/n), can someone explain that particular part for me please?
I used the property:

$a^c\cdot b^{-c}=\frac{a^c}{b^c}=$$\frac{a}{b}$$^c$

 June 21st, 2013, 03:12 PM #9 Senior Member   Joined: Sep 2012 From: British Columbia, Canada Posts: 764 Thanks: 53 Re: help me solve this please, I need the steps!! I understand how your method works. I'm just addressing a typo you made when you got from $\sqrt{n^2}=45.5$ to $n=225$
June 21st, 2013, 03:15 PM   #10
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Re: help me solve this please, I need the steps!!

Quote:
 Originally Posted by eddybob123 I understand how your method works. I'm just addressing a typo you made when you got from $\sqrt{n^2}=45.5$ to $n=225$
That's $45\cdot5$ not $45.5$.

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