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# If r > 0, s ≠ 1/2 and r = 3s +1/1-2s, then s=

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Kudos [?]: 965 [0], given: 4466

If r > 0, s ≠ 1/2 and r = 3s +1/1-2s, then s= [#permalink]  15 Jun 2017, 08:07
Expert's post
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Question Stats:

77% (01:31) correct 22% (00:49) wrong based on 22 sessions

If $$r > 0$$, s ≠ $$\frac{1}{2}$$ and $$r = \frac{3s +1}{1-2s}$$, then $$s=$$

A) $$\frac{3r}{12 +6r}$$

B) $$\frac{-2r}{3}$$

C) $$\frac{r-1}{3+2r}$$

D) $$\frac{2}{3(1-r)}$$

E) $$\frac{-1+r}{3}$$
[Reveal] Spoiler: OA

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GRE Instructor
Joined: 10 Apr 2015
Posts: 1169
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Kudos [?]: 1039 [1] , given: 6

Re: If r > 0, s ≠ 1/2 and r = 3s +1/1-2s, then s= [#permalink]  15 Jun 2017, 13:41
1
KUDOS
Expert's post
Carcass wrote:

If $$r > 0$$, s ≠ $$\frac{1}{2}$$ and $$r = \frac{3s +1}{1-2s}$$, then $$s=$$

A) $$\frac{3r}{12 +6r}$$

B) $$\frac{-2r}{3}$$

C) $$\frac{r-1}{3+2r}$$

D) $$\frac{2}{3(1-r)}$$

E) $$\frac{-1+r}{3}$$

Given: $$r = \frac{3s +1}{1-2s}$$

Multiply both sides by (1 - 2s) to get: r(1 - 2s) = 3s + 1
Expand: r - 2rs = 3s + 1
NOTE: We want the s's on one side. So....
Add 2rs to both sides: r = 3s + 2rs + 1
Subtract 1 from both sides: r - 1 = 3s + 2rs
Factor right side: r - 1 = s(3 + 2r)
Divide both sides by (3 + 2r) to get: (r - 1)/(3 + 2r) = s

[Reveal] Spoiler:
C

Cheers,
Brent
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Brent Hanneson – Creator of greenlighttestprep.com

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Re: If r > 0, s ≠ 1/2 and r = 3s +1/1-2s, then s=   [#permalink] 15 Jun 2017, 13:41
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# If r > 0, s ≠ 1/2 and r = 3s +1/1-2s, then s=

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