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If V = 12R / (r + R) , then R = A. Vr / (12 - V) B. Vr + V /12 C. V

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If V = 12R / (r + R) , then R = A. Vr / (12 - V) B. Vr + V /12 C. V  [#permalink]

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12 Feb 2017, 03:45
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Difficulty:

15% (low)

Question Stats:

86% (01:22) correct 14% (04:08) wrong based on 36 sessions

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Source: Major Tests

If V = 12R / (r + R) , then R =

A. Vr / (12 - V)
B. Vr + V /12
C. Vr - 12
D. V / r - 12
E. V (r + 1) /12

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Re: If V = 12R / (r + R) , then R = A. Vr / (12 - V) B. Vr + V /12 C. V  [#permalink]

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12 Feb 2017, 05:29
Source: Major Tests

If V = 12R / (r + R) , then R =

A. Vr / (12 - V)
B. Vr + V /12
C. Vr - 12
D. V / r - 12
E. V (r + 1) /12

Hey,

PFB the solution.

This is a simple re-arrangement question.

• $$V = \frac{12R}{(r + R)}$$

• Multiplying both sides by $$(r + R)$$, we get -

o $$V * (r + R) = 12R * \frac{(r+R)}{(r+R)}$$

o $$Vr + VR = 12R$$

o Subtracting both sides by $$VR$$, we get –

 $$Vr + VR – VR = 12R – VR$$

 Therefore, $$R = \frac{Vr}{(12- V)}$$

o Correct Answer is Option A

Thanks,
Saquib
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Re: If V = 12R / (r + R) , then R = A. Vr / (12 - V) B. Vr + V /12 C. V  [#permalink]

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12 Feb 2017, 05:51
Source: Major Tests

If V = 12R / (r + R) , then R =

A. Vr / (12 - V)
B. Vr + V /12
C. Vr - 12
D. V / r - 12
E. V (r + 1) /12

$$rV + RV = 12R$$

Or, $$12R - RV = rV$$

Or, $$R ( 12 - V ) = rV$$

Or, $$R = \frac{rV}{(12 - V)}$$

Hence, correct answer will be (A) Vr / (12 - V)
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Re: If V = 12R / (r + R) , then R = A. Vr / (12 - V) B. Vr + V /12 C. V  [#permalink]

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12 Feb 2017, 20:16
1

This question can be solved by TESTing VALUES.

We're told that V = 12R / (r + R) and we're asked for the value of R.

IF....
R = 2
r = 4
V = (12)(2)/(4+2) = 24/6 = 4

So we're looking for an answer that equals 2 when r = 4 and V = 4

Answer A: 16/8 = 2 This IS a match
Answer B: 16 + 4/12 = 16 1/3 NOT a match
Answer C: 16 - 12 = 4 NOT a match
Answer D: 4/4 - 12 = -11 NOT a match
Answer E: 4(5)/12 = 20/12 NOT a match

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Re: If V = 12R / (r + R) , then R = A. Vr / (12 - V) B. Vr + V /12 C. V  [#permalink]

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19 Feb 2017, 10:56
But I doubt it that it is of 600 level man
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Got Q42,V17
Target#01 Q45,V20--April End

Re: If V = 12R / (r + R) , then R = A. Vr / (12 - V) B. Vr + V /12 C. V &nbs [#permalink] 19 Feb 2017, 10:56
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