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In the rectangular coordinate system, are the points (r,s)

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In the rectangular coordinate system, are the points (r,s) [#permalink]

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In the rectangular coordinate system, are the points (r,s) and (u,v) equidistant from the origin?

(1) r + s = 1

(2) u = 1 - r and v = 1 - s

OPEN DISCUSSION OF THIS QUESTION IS HERE: in-the-rectangular-coordinate-system-are-the-points-r-s-92823.html

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Re: In the rectangular coordinate system, are the points (r,s) [#permalink]

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New post 03 Sep 2009, 03:13
Most discussed GPrep Q

you need to prove

r^2 + s^2 = u^2 + v^2

hence you need both the (1) and (2)

CasperMonday wrote:
Image


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Re: In the rectangular coordinate system, are the points (r,s) [#permalink]

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New post 03 Sep 2009, 03:17
My solution is:

the distance of the first point from the origin is \(r^2+s^2\)
the distance of the second point is \(u^2+v^2\)
the question is actually asking is \(r^2+s^2=u^2+v^2\)?

(1) \(r+s=1\)
apparently, insufficient. we know nothing about \(u\) and \(v\)

(2) \(u=1-r\) and \(v=1-s\)
might be sufficient but we should check by substituting for \(u\), \(v\) in the original equation:
\(r^2+s^2=(1-r)^2+(1-s)^2\)
by simplifying the equation we get:
\(r^2+s^2=r^2+s^2-2(r+s)+2\)
this doesn't allow us to make any conclusions. hence, insufficient

by combining (1) and (2), we get that
\((1-s)^2+s^2=((1-s)^2+s^2-2((1-s)+s)+2\)
simplifying,
\(1-2s+2s^2=1-2s+2s^2\)

final answer is C.

but i am wondering if there are other approaches to this problem. thank for contributions.
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Re: In the rectangular coordinate system, are the points (r,s) [#permalink]

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New post 03 Sep 2009, 03:19
nitya34 wrote:
Most discussed GPrep Q

you need to prove

r^2 + s^2 = u^2 + v^2

hence you need both the (1) and (2)


i was typing my answer right when you posted yours. as i said i am interested in other methods to solve the prob.))
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Re: In the rectangular coordinate system, are the points (r,s) [#permalink]

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New post 03 Sep 2009, 03:40
same strategy as yours with slight modification

we need to prove r^2+s^2=u^2+v^2

now r^2+s^2=(1-u)^2 + (1-v)^2= 2-2(u+v)+(u^2+v^2)

Now from (1) and (2) u+v=1+1-(r+s) = 2-1=1

hence r^2+s^2=u^2+v^2
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Re: In the rectangular coordinate system, are the points (r,s) [#permalink]

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New post 01 Oct 2009, 13:17
How can you say \(r^2+s^2\). it must be sqrt of (\(r^2+s^2\))........thank god I got it after lot of efforts

CasperMonday wrote:
My solution is:

the distance of the first point from the origin is \(r^2+s^2\)
the distance of the second point is \(u^2+v^2\)
the question is actually asking is \(r^2+s^2=u^2+v^2\)?

(1) \(r+s=1\)
apparently, insufficient. we know nothing about \(u\) and \(v\)

(2) \(u=1-r\) and \(v=1-s\)
might be sufficient but we should check by substituting for \(u\), \(v\) in the original equation:
\(r^2+s^2=(1-r)^2+(1-s)^2\)
by simplifying the equation we get:
\(r^2+s^2=r^2+s^2-2(r+s)+2\)
this doesn't allow us to make any conclusions. hence, insufficient

by combining (1) and (2), we get that
\((1-s)^2+s^2=((1-s)^2+s^2-2((1-s)+s)+2\)
simplifying,
\(1-2s+2s^2=1-2s+2s^2\)

final answer is C.

but i am wondering if there are other approaches to this problem. thank for contributions.
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Re: In the rectangular coordinate system, are the points (r,s) [#permalink]

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New post 02 Oct 2009, 08:13
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Re: In the rectangular coordinate system, are the points (r,s) [#permalink]

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New post 07 Sep 2010, 06:51
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mrsmarthi wrote:


Hey guyz

I am not master of quant either verbal:) but i did this question really quick.Maybe lucky.

a) R+S=1 (no info about U and V then insufficient)

b) u+r=1, v+s=1 not sufficent

Together

U+R= R+S

U=S

and

V+S=R+S

V=R

if U=S and V=R they are equidistant from the orgin.


PS: I did like that cuz i couldnt remember the main formula however it is more quick
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Re: In the rectangular coordinate system, are the points (r,s) [#permalink]

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New post 07 Sep 2010, 07:09
C.

Find the distance of U,V from origin. Substitute U = 1-R and V = 1-S. You will notice that when R+S=1 this distance equals the distance of R,S from origin.
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Re: In the rectangular coordinate system, are the points (r,s) [#permalink]

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New post 07 Sep 2010, 07:36
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CasperMonday wrote:
Image

OA

In the rectangular coordinate system, are the points (r,s) and (u,v) equidistant from the origin?

(1) r + s = 1

(2) u = 1 - r and v = 1 - s

Distance between the point A (x,y) and the origin can be found by the formula: \(D=\sqrt{x^2+y^2}\).

Basically the question asks is \(\sqrt{r^2+s^2}=\sqrt{u^2+v^2}\) OR is \(r^2+s^2=u^2+v^2\)?

(1) \(r+s=1\), no info about \(u\) and \(v\);

(2) \(u=1-r\) and \(v=1-s\) --> substitute \(u\) and \(v\) and express RHS using \(r\) and \(s\) to see what we get: \(RHS=u^2+v^2=(1-r)^2+(1-s)^2=2-2(r+s)+ r^2+s^2\). So we have that \(RHS=u^2+v^2=2-2(r+s)+ r^2+s^2\) and thus the question becomes: is \(r^2+s^2=2-2(r+s)+ r^2+s^2\)? --> is \(r+s=1\)? We don't know that, so this statement is not sufficient.

(1)+(2) From (2) question became: is \(r+s=1\)? And (1) says that this is true. Thus taken together statements are sufficient to answer the question.

Answer: C.

Hope it helps.
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Re: In the rectangular coordinate system, are the points (r,s) [#permalink]

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New post 10 Sep 2010, 15:09
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We need to check whether r^2 + s^2 = u^2 + v^2
=> is \((r-u)* (r+u) = (v-s)* (v+s)\) ------------------------------A

Statement 1: Apparently Insufficient as no information about u and v

Statement 2:

Given \(u = 1 - r\) and \(v = 1 - s\) ---------------------B

=> \(r+u =1\) and \(v+s = 1\)------------------------------C

Using equations A and C
we need to check if \(u-r = s-v\)

if \(u+v = r+s\)

if \(u+v = r+s = 1-r + 1-s\)

if \(r+s = 1\) ----------------------------------D
Not Sufficient.

combine statement 1 and equations D , we can prove the distance is same.
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Re: In the rectangular coordinate system, are the points (r,s) [#permalink]

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New post 21 Oct 2010, 23:53
Was about to post this. I'm glad I checked before I did.

Thanks for the explanations!
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Re: In the rectangular coordinate system, are the points (r,s) [#permalink]

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New post 03 Dec 2017, 11:15
CasperMonday wrote:
In the rectangular coordinate system, are the points (r,s) and (u,v) equidistant from the origin?

(1) r + s = 1

(2) u = 1 - r and v = 1 - s



OPEN DISCUSSION OF THIS QUESTION IS HERE: in-the-rectangular-coordinate-system-are-the-points-r-s-92823.html

--== 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.

_________________

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GMAT Math Book | Triangles | Polygons | Coordinate Geometry | Factorials | Circles | Number Theory | Remainders; 8. Overlapping Sets | PDF of Math Book; 10. Remainders | GMAT Prep Software Analysis | SEVEN SAMURAI OF 2012 (BEST DISCUSSIONS) | Tricky questions from previous years.

Collection of Questions:
PS: 1. Tough and Tricky questions; 2. Hard questions; 3. Hard questions part 2; 4. Standard deviation; 5. Tough Problem Solving Questions With Solutions; 6. Probability and Combinations Questions With Solutions; 7 Tough and tricky exponents and roots questions; 8 12 Easy Pieces (or not?); 9 Bakers' Dozen; 10 Algebra set. ,11 Mixed Questions, 12 Fresh Meat

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Re: In the rectangular coordinate system, are the points (r,s)   [#permalink] 03 Dec 2017, 11:15
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