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If P(r)=8r/(1-r), for what value of r does P(r)=1/2(P(3))?

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If P(r)=8r/(1-r), for what value of r does P(r)=1/2(P(3))?  [#permalink]

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New post Updated on: 18 Sep 2018, 21:05
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If \(P(r)=\frac{8r}{(1-r)}\), for what value of r does \(P(r)=\frac{1}{2}P(3)\)?

A. 6
B. 3
C. 0
D. –3
E. –6

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Originally posted by monir6000 on 20 May 2012, 01:38.
Last edited by Bunuel on 18 Sep 2018, 21:05, edited 2 times in total.
Edited the question and added the OA
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Re: If P(r)=8r/(1-r), for what value of r does P(r)=1/2(P(3))?  [#permalink]

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New post 20 May 2012, 04:21
7
monir6000 wrote:
If P(r)=8r/(1-r), for what value of r does P(r)=1/2*(P(3))?

A. 6
B. 3
C. 0
D. –3
E. –6


P(r) = 8r / (1-r)

P(3) = 8*3 / ( 1-3 ) = - 12

1/2 * P(3) = - 6

P(r) = - 6

=> 8r / ( 1-r ) = - 6

=> 8r = 6r - 6

=> 2r = - 6

=> r = - 3
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Re: If P(r)=8r/(1-r), for what value of r does P(r)=1/2(P(3))?  [#permalink]

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New post 17 Oct 2014, 07:00
Rca wrote:
If P(r)=8r/(1-r), for what value of r does P(r)=1/2(P(3))?

A. 6
B. 3
C. 0
D. –3
E. –6

Can someone explain this problem again? I got it till -12, but wasn't sure what to do after this? Thanks in advance!


\(P(r) = \frac{8r}{1-r}\), so \(P(3) = \frac{8*3}{1-3} = - 12\).

We need to find for what value of r does \(P(r)=\frac{1}{2}*P(3)\), so for what value of r does \(P(r)=\frac{1}{2}*(-12)\). So, we soulh solve for r the following: \(\frac{8r}{1-r}=\frac{1}{2}*(-12)\) --> \(r=-3\).

Answer: D.

Check questions about functions in Special Questions Directory:

Operations/functions defining algebraic/arithmetic expressions
Symbols Representing Arithmetic Operation
Rounding Functions
Various Functions

Hope this helps.
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Re: If P(r)=8r/(1-r), for what value of r does P(r)=1/2(P(3))?  [#permalink]

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New post 18 Sep 2018, 21:02
I have a question.
Isn't it kind of confusing,
P(r)=1/2(P(3)) could be
either
P(r)=1/(2(P(3)))
or
P(r)=(1/2)(P(3))
?
how do you guys know it is P(r)=(1/2)(P(3))?
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If P(r)=8r/(1-r), for what value of r does P(r)=1/2(P(3))?  [#permalink]

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New post 18 Sep 2018, 21:13
Xica wrote:
I have a question.
Isn't it kind of confusing,
P(r)=1/2(P(3)) could be
either
P(r)=1/(2(P(3)))
or
P(r)=(1/2)(P(3))
?
how do you guys know it is P(r)=(1/2)(P(3))?


Hi Xica,
Notice that P(r)=\(\frac{1}{2}\)*P(3) is given in the question stem.

All other equations furnished are assumptions at your end.

You see that P(r)=\(\frac{1}{2P(3)}\) is different from what has been given in question stem.

You may raise further queries (if any).
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If P(r)=8r/(1-r), for what value of r does P(r)=1/2(P(3))? &nbs [#permalink] 18 Sep 2018, 21:13
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