prob X-by : PS Archive
Check GMAT Club App Tracker for the Latest School Decision Releases http://gmatclub.com/AppTrack

 It is currently 02 Dec 2016, 17:03

### GMAT Club Daily Prep

#### Thank you for using the timer - this advanced tool can estimate your performance and suggest more practice questions. We have subscribed you to Daily Prep Questions via email.

Customized
for You

we will pick new questions that match your level based on your Timer History

Track

every week, we’ll send you an estimated GMAT score based on your performance

Practice
Pays

we will pick new questions that match your level based on your Timer History

# Events & Promotions

###### Events & Promotions in June
Open Detailed Calendar

# prob X-by

Author Message
Senior Manager
Joined: 27 May 2009
Posts: 281
Followers: 2

Kudos [?]: 333 [0], given: 18

### Show Tags

30 Aug 2009, 11:11
00:00

Difficulty:

(N/A)

Question Stats:

0% (00:00) correct 0% (00:00) wrong based on 0 sessions

### HideShow timer Statistics

This topic is locked. If you want to discuss this question please re-post it in the respective forum.

OA = 1/6 how???
Attachments

prepprob.jpg [ 21.49 KiB | Viewed 828 times ]

Manager
Joined: 10 Aug 2009
Posts: 130
Followers: 3

Kudos [?]: 64 [0], given: 10

### Show Tags

30 Aug 2009, 12:26
You have 4C2=6 different products of 2 numbers.
If you write down this six options and simplify, you will see that only one option fits the give expression.
this option is $$(x-y)\times (x+y)=x^2-y^2$$...All other products will be of incorrect form.
Hence the prob = 1/6
Manager
Joined: 25 Aug 2009
Posts: 176
Followers: 1

Kudos [?]: 88 [0], given: 12

### Show Tags

30 Aug 2009, 16:42
total possibilities = $$4C2$$ = 6

Only one selection yields the favorable outcome i.e. (x + y) and (x - y) = 1

Prob. = 1/6
Manager
Joined: 05 Jul 2009
Posts: 182
Followers: 1

Kudos [?]: 46 [0], given: 5

### Show Tags

30 Aug 2009, 20:13
This is not a data sufficiency problem. Posted in the wrong section.
Math Expert
Joined: 02 Sep 2009
Posts: 35837
Followers: 6827

Kudos [?]: 89650 [0], given: 10380

### Show Tags

04 Sep 2009, 18:53
LenaA wrote:
You have 4C2=6 different products of 2 numbers.
If you write down this six options and simplify, you will see that only one option fits the give expression.
this option is $$(x-y)\times (x+y)=x^2-y^2$$...All other products will be of incorrect form.
Hence the prob = 1/6

Think it's not necessary to write down six options, x^2-(bx)^2=(x+bx)(x-bx)
We can see that there is only one pair like this one: (x+y)(x-y).

_________________
Re: prob X-by   [#permalink] 04 Sep 2009, 18:53
Display posts from previous: Sort by