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c and d are positive [#permalink]
25 Apr 2017, 02:58
Question Stats:
48% (00:48) correct
51% (01:16) wrong based on 173 sessions
c and d are positive \(\frac{1}{c} = 1 + \frac{1}{d}\)
Quantity A 
Quantity B 
c 
d 
A) Quantity A is greater. B) Quantity B is greater. C) The two quantities are equal. D) The relationship cannot be determined from the information given.
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Re: c and d are positive [#permalink]
26 May 2017, 12:00
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Carcass Array[WROTE]: c and d are positive \(\frac{1}{c} = 1 + \frac{1}{d}\)
Quantity A 
Quantity B 
c 
d 
A) Quantity A is greater. B) Quantity B is greater. C) The two quantities are equal. D) The relationship cannot be determined from the information given. Given: 1/c = 1 + 1/d Rewrite 1 as d/d to get: 1/c = d/d + 1/d Combine fractions to get: 1/c = (d + 1)/d Flip both fractions to get: c/1 = d/(d+1) In other words, c = d/(d+1) In Quantity A, replace c with d/(d+1) to get: Quantity A: d/(d+1) Quantity B: d Since d is positive, we know that d+1 is positive. So, let's multiply both quantities by (d+1) to get: Quantity A: d Quantity B: d² + d Subtract d from both quantities to get: Quantity A: 0 Quantity B: d² Since d is not equal to zero, we know that d² is POSITIVE Answer: Cheers, Brent
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Re: c and d are positive [#permalink]
01 Apr 2018, 12:51
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Answer: B 1/c equals 1 + 1/d so 1/c is something bigger than 1/d, 1/c > 1/ d so d > c
EVEN for negative values this correlation is true.
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Re: c and d are positive [#permalink]
04 Apr 2018, 07:46
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Fraction 1/c is bigger than fraction 1/d as we have to add something to fraction 1/d to make it equal to fraction 1/c.
So, if 1/c > 1/d then c < d
Ans: B



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Re: c and d are positive [#permalink]
16 Sep 2018, 23:10
Plug in +ve fraction values:
01/41/4 +1 1/d 1/c
1/4 < 5/4 < 1/d < 1/c BUT 4> 4/5 > d> c Qty B > Qty A



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Re: c and d are positive [#permalink]
14 Dec 2018, 19:45
Carcass Array[WROTE]: c and d are positive \(\frac{1}{c} = 1 + \frac{1}{d}\)
Quantity A 
Quantity B 
c 
d 
A) Quantity A is greater. B) Quantity B is greater. C) The two quantities are equal. D) The relationship cannot be determined from the information given. There is an inherent contradiction in the given information, leading me to get the problem wrong. Let me explain. Let's simplify the equation given. First we multiply everything by c and get 1 = c + c/d Next we multiply by d d = cd + c dcd = c d(1c) = c d = c/(1c) If c is positive, then the 1c in the denominator will be negative. Thus, d is negative. Thereby leading to a contradiction.



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Re: c and d are positive [#permalink]
15 Dec 2018, 06:42
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QuantumWonder Array[WROTE]: Carcass Array[WROTE]: c and d are positive \(\frac{1}{c} = 1 + \frac{1}{d}\)
Quantity A 
Quantity B 
c 
d 
A) Quantity A is greater. B) Quantity B is greater. C) The two quantities are equal. D) The relationship cannot be determined from the information given. There is an inherent contradiction in the given information, leading me to get the problem wrong. Let me explain. Let's simplify the equation given. First we multiply everything by c and get 1 = c + c/d Next we multiply by d d = cd + c dcd = c d(1c) = c d = c/(1c) If c is positive, then the 1c in the denominator will be negative. Thus, d is negative. Thereby leading to a contradiction. If c is positive, the denominator isn't necessarily negative. For example, if c = 1/2, then d = 1 Cheers, Brent
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Re: c and d are positive [#permalink]
15 Dec 2018, 17:10
GreenlightTestPrep Array[WROTE]: QuantumWonder Array[WROTE]: Carcass Array[WROTE]: c and d are positive \(\frac{1}{c} = 1 + \frac{1}{d}\)
Quantity A 
Quantity B 
c 
d 
A) Quantity A is greater. B) Quantity B is greater. C) The two quantities are equal. D) The relationship cannot be determined from the information given. There is an inherent contradiction in the given information, leading me to get the problem wrong. Let me explain. Let's simplify the equation given. First we multiply everything by c and get 1 = c + c/d Next we multiply by d d = cd + c dcd = c d(1c) = c d = c/(1c) If c is positive, then the 1c in the denominator will be negative. Thus, d is negative. Thereby leading to a contradiction. If c is positive, the denominator isn't necessarily negative. For example, if c = 1/2, then d = 1 Cheers, Brent Thank you! That must have been from stress, can't believe I didn't see that. It's silly that it slipped me, double major in physics and mathematics and still have things like that slip me haha. GRE really challenges you to think very carefully, I like that aspect.



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Re: c and d are positive [#permalink]
15 Dec 2018, 21:44
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Think of this
c and d are positive numbers
1/c > 1+1/d
this means that C is a positive fraction less than 1, since we can only get a number greater than 1 if 1 is divided by something smaller than 1. if c is super small, like .01 then
100 > 1+1/d
d cant be less than or equal to .01.. if it is then
100 > 1+1/.01 becomes 100 > 1 + 100... which is not true so we know that if c is equal to .01, then d has to be greater than .01 thus, d is greater than c.
The answer is B



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Re: c and d are positive [#permalink]
17 Dec 2018, 03:39
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given:1/c=1+1/d solving equation gives d=cd+c This implies D is Cd times greater than C



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Re: c and d are positive [#permalink]
17 Dec 2018, 07:17
vigjna Array[WROTE]: given:1/c=1+1/d solving equation gives d=cd+c This implies D is Cd times greater than C Nice fast solution mate.




Re: c and d are positive
[#permalink]
17 Dec 2018, 07:17





