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# if AB is not equal to 0, then a^-1 + b^-1 = 1) a+b 2 -(a+b)

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Intern
Joined: 07 Sep 2007
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if AB is not equal to 0, then a^-1 + b^-1 = 1) a+b 2 -(a+b) [#permalink]  18 Sep 2007, 09:04
if AB is not equal to 0, then a^-1 + b^-1 =

1) a+b
2 -(a+b)
3) 1/a+b
4) 2/a+b
5) a+b/ab

The answer is 5, but I thought it was 3...can someone explain?
Senior Manager
Joined: 27 Aug 2007
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5, don't understand what you didnot understand???
CEO
Joined: 29 Mar 2007
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Re: GMATPrep Question [#permalink]  18 Sep 2007, 09:24
spf wrote:
if AB is not equal to 0, then a^-1 + b^-1 =

1) a+b
2 -(a+b)
3) 1/a+b
4) 2/a+b
5) a+b/ab

The answer is 5, but I thought it was 3...can someone explain?

simple:

a^-1 +b^-1 ---> 1/a+1/b --->make common denominators---> b/ab+a/ab = a+b/ab u don't combine the common denominators i.e. don't make it 2ab or ab +ab etc...

just ab.

ans E, er 5.
Intern
Joined: 07 Sep 2007
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thanks, I thought it was

a^-1 and b^-1 which is equal to 1/a + 1/b

which equals

1/a+b
Director
Joined: 08 Jun 2007
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spf wrote:
thanks, I thought it was

a^-1 and b^-1 which is equal to 1/a + 1/b

which equals

1/a+b

spf
1/a + 1/b
which equals
1/a+b

--> this is blasphemy here!

just kidding ...if you were confused its fine...if you didnt know this then I would suggest get quant basics straight ..just a friendly advice.
Manager
Joined: 04 Sep 2007
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spf wrote:
thanks, I thought it was

a^-1 and b^-1 which is equal to 1/a + 1/b

which equals

1/a+b

geez.. Looks like you need to get back to your basics and refresh yourself about the fractions and their properties.

You are scaring me with that statement (1/a + 1/b) = 1/a+b)

Sorry if I come across as annoying, but I'm serious here. Were you joking when you wrote that?
Manager
Joined: 20 Dec 2004
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Mate you need to get your fundas clear. I am not sure if this is a joke or this is for real. How can you conclude I/a + 1/b = 1/a+b. I would recommend going through Algebra basics.
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Regards

Subhen

Senior Manager
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subhen wrote:
Mate you need to get your fundas clear. I am not sure if this is a joke or this is for real. How can you conclude I/a + 1/b = 1/a+b. I would recommend going through Algebra basics.

I feel this is too harsh on the original poster. You need to understand that the OP would learn only thru such posts. Please note that all of us have our respective weaknesses. Some may be weak in math and some may be weak in verbal. So please do not discourage the original poster.

Please note that I have seen some disgusting verbal answers from people who are stars in quant. I hope you guys get the point.
Director
Joined: 17 Sep 2005
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dahcrap wrote:
subhen wrote:
Mate you need to get your fundas clear. I am not sure if this is a joke or this is for real. How can you conclude I/a + 1/b = 1/a+b. I would recommend going through Algebra basics.

I feel this is too harsh on the original poster. You need to understand that the OP would learn only thru such posts. Please note that all of us have our respective weaknesses. Some may be weak in math and some may be weak in verbal. So please do not discourage the original poster.

Please note that I have seen some disgusting verbal answers from people who are stars in quant. I hope you guys get the point.

Hey spf,

I hope you have not taken suben's comment at your heart.
He might have written his comments in hurry without looking at the tone.....
You are welcome to this forum and you can throw your smallest doubts here for the clarifications.

Cheers!!
- Brajesh
Manager
Joined: 04 Sep 2007
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wizardofwashington wrote:
spf wrote:
thanks, I thought it was

a^-1 and b^-1 which is equal to 1/a + 1/b

which equals

1/a+b

geez..

You are scaring me with that statement (1/a + 1/b) = 1/a+b)

Sorry if I come across as annoying, but I'm serious here. Were you joking when you wrote that?

I apologize for being a bit harsh on you SPF. I tend to forget that we all started somewhere on this journey, asking the questions like yours. So, I think it was inappropriate for me to suggest you to get your basics right . I got no right to say such things.

Sorry if I came across offensively with the use of words akin to Shuben's (bot a lot subtle) and in no way my words are meant to be offensive. As "DahCrap" noted, you are welcome and please continue to share your questions, good or bad, silly or excellent, with folks around. Probably the best way to learn - by making mistakes and learning where you made the mistakes.
Manager
Joined: 20 Dec 2004
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Hi SPF,

My apologies as well if my comments came across to you as being rude. It was not meant to be. I guess we are all at different stages of preparation. As such the concepts that might seem easy for some of us maybe difficult for some who are just starting their prepration.

All the best for your preparation.
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Regards

Subhen

CEO
Joined: 29 Mar 2007
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Hey man I really reccomend that you learn your basics as everyone here has suggested.

Additionally, I reccomend that you don't spend a lot of time on the math forums. Unless you have a specific question, attempting to answer these questions at your level can be a real confindence killer. The majority of the questions posted are among the hardest, so learn ur basics and then come back and try!

Good luck.
Intern
Joined: 07 Sep 2007
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It was a complete oversight and obvisouly a dumb error. I did not look it over prior to the post. Thanks for the help.
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