Target Test Prep 20% Off Flash Sale is on! Code: FLASH20

Redeem
Target Test Prep Flash Sale
Target Test Prep is 20% off right now!
Use code FLASH20

Available with Beat the GMAT members only code

MORE DETAILS
Magoosh
Magoosh
Study with Magoosh GMAT prep

Available with Beat the GMAT members only code

MORE DETAILS
Magoosh

OG DS #57

This topic has expert replies
Post new topic Post Reply
Previous Topic Next Topic
Senior | Next Rank: 100 Posts
Posts: 65
Joined: Tue Jun 12, 2007 12:57 am

OG DS #57

by erdnah » Wed Jul 18, 2007 7:14 am
Hi,

I've got a question; perhaps some can help me with that?! :?

Image

With my last operation I got x+y=0, thus at least A or D would have to be correct...

erdnah
Top
Senior | Next Rank: 100 Posts
Posts: 62
Joined: Fri Jul 13, 2007 2:06 pm

by chatekar » Wed Jul 18, 2007 7:52 am
erdnah,

To find the value of 1/X + 1/Y i.e. (X+Y)/XY, so you need two things,
first is X+Y and the second is XY.

Both are given in statement 1 and 2 so you need both the statements together.

Hope this helps

Thanks
Top
Senior | Next Rank: 100 Posts
Posts: 65
Joined: Tue Jun 12, 2007 12:57 am

by erdnah » Wed Jul 18, 2007 7:55 am
@chatekar, yeah, i found that information also in the og :)

but what i really want to know is, why i can't multiply the last term with xy, so that i would get x+y = 0!? i feel terrible stupid :x
Top
Senior | Next Rank: 100 Posts
Posts: 62
Joined: Fri Jul 13, 2007 2:06 pm

by chatekar » Wed Jul 18, 2007 8:27 am
If you are multiplying by xy to get the value of the given expression, then you are changing the value of the given expression.
You can't simply multiply by xy, you also need to divide by xy so that value of the expression doesn't change.

Am I making sense?

Thanks
Top
Senior | Next Rank: 100 Posts
Posts: 65
Joined: Tue Jun 12, 2007 12:57 am

by erdnah » Wed Jul 18, 2007 10:59 am
Yeah, of course you do... :roll:
There are days, I should have stayed in bed. :wink:
Top
Senior | Next Rank: 100 Posts
Posts: 65
Joined: Tue Jun 12, 2007 12:57 am

OG DS #56

by erdnah » Fri Jul 20, 2007 9:32 am
It seems as if I did the same mistake today again :roll:

When there is x = x², I divided both sides by x. I though I would get 1 = x which seemed to be wonderful in my eyes... but x could also be 0!

What was this time (or as on the problem above) my mistake in thinking?

Hope someone can help me..
Top
Senior | Next Rank: 100 Posts
Posts: 54
Joined: Mon Aug 06, 2007 12:04 pm

Re: OG DS #56

by bingojohn » Tue Aug 07, 2007 10:59 am
erdnah wrote:It seems as if I did the same mistake today again :roll:

When there is x = x², I divided both sides by x. I though I would get 1 = x which seemed to be wonderful in my eyes... but x could also be 0!

What was this time (or as on the problem above) my mistake in thinking?

Hope someone can help me..
Solve equation:

x^2 = x
x^2 - x = 0
x(x - 1) = 0

x = 0 OR x = 1

hope this helps...
Top
Post new topic Post Reply
• Page 1 of 1