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# Square roots

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Senior Manager
Joined: 10 Mar 2008
Posts: 326

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03 Oct 2008, 12:06

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Director
Joined: 27 Jun 2008
Posts: 505
WE 1: Investment Banking - 6yrs

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03 Oct 2008, 12:29
D

I must confess, it took me a while to solve this, however, if its a "GMAT" problem, you should be able to solve it within 2 mins. So, I was rattling my brian.

Anyway, rt63 = 3rt7.

> ROOT 2rt63 + 2 / 8+rt63
> ROOT 8*2rt63 + rt63*rt63*2 + 2 / 8+rt63
> ROOT 16rt63 + 128 / 8+rt63
> ROOT 16(rt63 + 8) / (8 + rt63)
> ROOT 16 = 4
Manager
Joined: 27 Sep 2008
Posts: 76

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03 Oct 2008, 12:36
we know that 8+sqrt(63)/8+sqrt(63) = 1

so:

sqrt(2sqrt(63)+2/8+3*sqrt(7)) = x

2*sqrt(63)+2/8+3*sqrt(7) = x^2

2*sqrt(63)*1+2/8+sqrt(63) = x^2

2*sqrt(63)*(8+sqrt(63)/8+sqrt(63))+2/8+sqrt(63) = x^2

(2*sqrt(63)*(8+sqrt(63))+2)/8+sqrt(63) = x^2

(16*sqrt(63)+63*2+2)/8+sqrt(63) = x^2

16*sqrt(63)+128/8+sqrt(63) = x^2

16*(sqrt(63)+8)/(8+sqrt(63)) = x^2

16*1 = x^2

x = 4

Manager
Joined: 25 Aug 2008
Posts: 182
Location: India
WE 1: 3.75 IT
WE 2: 1.0 IT

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06 Oct 2008, 02:42

And the calculation was even not that complex. You can solve it directly.
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Cheers,
Varun

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Retired Moderator
Joined: 05 Jul 2006
Posts: 1731

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06 Oct 2008, 03:01
vksunder wrote:

if GMAT is for business leaders , i will think like one and use approximation

sqrt(2sqrt63 + 2 / 8+3sqrt7)

sqrt 63 = approximately sqrt 64 = 8

sqrt 7 approx = sqrt 9 = 3

sqrt ( 2*8 + 2 / 3*3) = sqrt (16 + 2 /17) = sqrt ( 274/ 16) = sqrt 274 / sqrt 16 =

approx sqrt ( 16^2) / sqrt 16 = 16/4 = 4
Senior Manager
Joined: 10 Mar 2008
Posts: 326

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06 Oct 2008, 06:05
Very Good point yezz. Damn, I need to start thinking like a leader:)

--== Message from GMAT Club Team ==--

This is not a quality discussion. It has been retired.

If you would like to discuss this question please re-post it in the respective forum. Thank you!

To review the GMAT Club's Forums Posting Guidelines, please follow these links: Quantitative | Verbal Please note - we may remove posts that do not follow our posting guidelines. Thank you.
Re: Square roots &nbs [#permalink] 06 Oct 2008, 06:05
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# Square roots

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