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OA is "A". That's only A is sufficient. but I presume that that answer should be "C" because for me r=s , if I substitute in the equation then

1/r + 1/r = 2/r = 4 r = 1/2 and I am able to prove the condition. Although, OG has taken values of r and s to prove that 2nd condition is not sufficient, then why not try to put some values for r and s in the 1st option too? Please help

OA is "A". That's only A is sufficient. but I presume that that answer should be "C" because for me r=s , if I substitute in the equation then

1/r + 1/r = 2/r = 4 r = 1/2 and I am able to prove the condition. Although, OG has taken values of r and s to prove that 2nd condition is not sufficient, then why not try to put some values for r and s in the 1st option too? Please help

Question: is \frac{1}{r}+\frac{1}{s}=4 --> is \frac{r+s}{rs}=4 --> is r+s=4rs?

(1) r+s=4rs, directly answers the question. Sufficient. (2) r = s, the question becomes: is \frac{1}{r}+\frac{1}{r}=4 ? --> is r=\frac{1}{2}? but we dont' know whether r=\frac{1}{2}. Not sufficient.

Answer: A.

Hi Bunuel, Could you kindly explain statement 2 clearly. From the choice, we come to the conclusion that r=s=1/2. Cant this be sufficient to answer the question? In that case, it should be (D) right.????

The question asks: is \frac{1}{r}+\frac{1}{s}=4 ?

(2) says r = s. So, our questions becomes: is \frac{1}{r}+\frac{1}{r}=4? --> is r=\frac{1}{2}? Notice it's not given, in contrast we are asked to answer this.

Now, if r=\frac{1}{2}, then the answer is YES but if r\neq\frac{1}{2}, then the answer is NO. Do we know what r is actully equal to? No. So, this statement is NOT sufficient.

OA is "A". That's only A is sufficient. but I presume that that answer should be "C" because for me r=s , if I substitute in the equation then

1/r + 1/r = 2/r = 4 r = 1/2 and I am able to prove the condition. Although, OG has taken values of r and s to prove that 2nd condition is not sufficient, then why not try to put some values for r and s in the 1st option too? Please help

Question: is \frac{1}{r}+\frac{1}{s}=4 --> is \frac{r+s}{rs}=4 --> is r+s=4rs?

(1) r+s=4rs, directly answers the question. Sufficient. (2) r = s, the question becomes: is \frac{1}{r}+\frac{1}{r}=4 ? --> is r=\frac{1}{2}? but we dont' know whether r=\frac{1}{2}. Not sufficient.

Hi if i go the algebric way on statement 1 i get it right but statement 2 i get it wrong so I am kinda confused eg statement 2 sates r = s

so lets see 1/r + 1/s = 4 can be written as r + s = 4 rs so replacing r we get 2s = 4s^2 s = 1/2 so statement 2 is also sufficient hence ans is D but this is not correct _________________

OA is "A". That's only A is sufficient. but I presume that that answer should be "C" because for me r=s , if I substitute in the equation then

1/r + 1/r = 2/r = 4 r = 1/2 and I am able to prove the condition. Although, OG has taken values of r and s to prove that 2nd condition is not sufficient, then why not try to put some values for r and s in the 1st option too? Please help

Question: is \frac{1}{r}+\frac{1}{s}=4 --> is \frac{r+s}{rs}=4 --> is r+s=4rs?

(1) r+s=4rs, directly answers the question. Sufficient. (2) r = s, the question becomes: is \frac{1}{r}+\frac{1}{r}=4 ? --> is r=\frac{1}{2}? but we dont' know whether r=\frac{1}{2}. Not sufficient.

Answer: A.

Hi Bunuel, Could you kindly explain statement 2 clearly. From the choice, we come to the conclusion that r=s=1/2. Cant this be sufficient to answer the question? In that case, it should be (D) right.????

Re: If rs#0, is 1/r + 1/s = 4 ? [#permalink]
10 Aug 2014, 17:00

Hi Bunuel, Could you kindly explain statement 2 clearly. From the choice, we come to the conclusion that r=s=1/2. Cant this be sufficient to answer the question? In that case, it should be (D) right.????[/quote]

The question asks: is \frac{1}{r}+\frac{1}{s}=4 ?

(2) says r = s. So, our questions becomes: is \frac{1}{r}+\frac{1}{r}=4? --> is r=\frac{1}{2}? Notice it's not given, in contrast we are asked to answer this.

Now, if r=\frac{1}{2}, then the answer is YES but if r\neq\frac{1}{2}, then the answer is NO. Do we know what r is actully equal to? No. So, this statement is NOT sufficient.

Hope it's clear.[/quote]

Can you explain that please ? if we applied the second answer's approach on statement one :

if r= 1/2 and s=1/2 …….. > then r+s=4rs = 1/2 + 1/2 = 4*1/2*1/2 …. but if r=2 and s=2 the …> 2+2 not equal to 4*2*2

If rs#0, is 1/r + 1/s = 4 ? [#permalink]
12 Aug 2014, 07:04

Expert's post

shagalo wrote:

Can you explain that please ? if we applied the second answer's approach on statement one :

if r= 1/2 and s=1/2 …….. > then r+s=4rs = 1/2 + 1/2 = 4*1/2*1/2 …. but if r=2 and s=2 the …> 2+2 not equal to 4*2*2

this question is confusing !!!!!

Your question is not clear.

(1) says that r + s = 4rs. Why are you plugging number for which r + s does not equal to 4rs ? Also, the question asks whether r + s = 4rs and (1) directly answers this. Why even plug? _________________

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