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March 22nd, 2013, 09:52 AM   #1
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How does the text book come to its answer

Hi, I am trying to understand how they get 162.5mm as the answer. When I put this into the highlighted formula, I do not end up with 25? I am trying to get R on its own.

Luke
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March 22nd, 2013, 10:20 AM   #2
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Re: How does the text book come to its answer

Quote:
 Originally Posted by luke93 Hi, I am trying to understand how they get 162.5mm as the answer.
Given data is in m ; the 162.5 is in mm ; so doing the math should give .1625

I calculated it; ended up with SQRT(.6336 / 24) = ~.16248

.16248 / 1000 = 162.5 (rounded)

Ya'll ok now?

 March 22nd, 2013, 10:30 AM #3 Global Moderator     Joined: Oct 2008 From: London, Ontario, Canada - The Forest City Posts: 7,958 Thanks: 1146 Math Focus: Elementary mathematics and beyond Re: How does the text book come to its answer $25\,=\,\frac{r^2\,-\,0.0064}{r^2\,-\,0.0256} \\ 25r^2\,-\,25(0.0256)\,=\,r^2\,-\,0.0064 \\ 24r^2\,=\,-0.0064\,+\,25(0.0256) \\ r^2\,=\,\frac{0.6336}{24} \\ r\,=\,\sqrt{0.0264}\,\approx\,0.1625$
 March 22nd, 2013, 11:07 AM #4 Newbie   Joined: Mar 2013 Posts: 4 Thanks: 0 Re: How does the text book come to its answer Thank you both for the replies, it all makes sense now
March 22nd, 2013, 04:13 PM   #5
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Quote:
 Originally Posted by Denis .16248 / 1000 = 162.5 (rounded) Ya'll ok now?
.16248 * 1000 ... okay?

March 22nd, 2013, 04:25 PM   #6
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Re:

Quote:
Originally Posted by skipjack
Quote:
 Originally Posted by Denis .16248 / 1000 = 162.5 (rounded) Ya'll ok now?
.16248 * 1000 ... okay?
Aye, aye, Skipper! (first mistake this year )!

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