BREAKING: Target Test Prep releases Brand New 2026 On Demand GMAT prep course

Redeem

GMAT Prep

This topic has expert replies
Post new topic Post Reply
Previous Topic Next Topic
Senior | Next Rank: 100 Posts
Posts: 37
Joined: Sun Aug 26, 2007 3:45 pm
Thanked: 1 times

GMAT Prep

by Jameschan168 » Sun Sep 09, 2007 6:55 pm
If two of the four expressions x+y, x+5y, x-y, and 5x-y are chosen at random, what is the probability that their product will be in the form of x^2-(by)^2, where b is an integer?

a. 1/2
b. 1/3
c. 1/4
d. 1/5
e. 1/6

Answer is D
Top
Source: — Problem Solving |
Master | Next Rank: 500 Posts
Posts: 258
Joined: Mon Aug 27, 2007 12:43 pm
Thanked: 15 times

by ri2007 » Mon Sep 10, 2007 4:55 am
Hey

Can any one help with this one?

Thanks a lot
Top
Junior | Next Rank: 30 Posts
Posts: 24
Joined: Mon Jul 02, 2007 6:22 am

by karthick451 » Mon Sep 10, 2007 5:38 pm
i would go with 1/6 E as the answer.

since there are 4c2 ways of picking and there is only 1 pair that would not have any xy term.
Top
Master | Next Rank: 500 Posts
Posts: 258
Joined: Mon Aug 27, 2007 12:43 pm
Thanked: 15 times

by ri2007 » Mon Sep 10, 2007 6:47 pm
karthick451,

I got the same ans, but since Jameschan168 has given the ans to be D I was confused.

Jameschan168 can u pls check if u have given the wrong ans?

Thanks
Top
Master | Next Rank: 500 Posts
Posts: 460
Joined: Sun Mar 25, 2007 7:42 am
Thanked: 27 times

by samirpandeyit62 » Mon Sep 10, 2007 9:08 pm
I Agree with all of you

Here irrespective of the Order we select the expression the result will be as required.

so we have 1/4c2 =1/6

I think ans should be E
Regards
Samir
Top
Post new topic Post Reply
• Page 1 of 1