the remaining four incorrect choices

Expert replies

sanju09: GMAT Instructor; Posts: 3650; Joined: Wed Jan 21, 2009 4:27 amFollowed by: 80 members; Location: India; Thanked: 267 times; GMAT Score:760

by sanju09 » Wed Mar 31, 2010 2:24 am

I have an interesting case for all of you to deal with, at first sight, this is absolutely NOT a GMAT problem, but if I want to convert it to a hardly possible GMAT PS, then what special care in the answer choices must I take so that the remaining four incorrect choices can be easily deleted?

A bag contains n red balls, 2 n white balls, and 3 n black balls; all of same size. If the probability of randomly drawing n balls of same color from the bag is 1/6, then what is the least possible number of red balls in the bag?
(A) A
(B) B
(C) C
(D) D
(E) E

NO KIDDING

The mind is everything. What you think you become. –Lord Buddha

Sanjeev K Saxena
Quantitative Instructor
The Princeton Review - Manya Abroad
Lucknow-226001

www.manyagroup.com

Source: Beat The GMAT — Quantitative Reasoning | Wed Mar 31, 2010 2:24 am

kstv: Legendary Member; Posts: 610; Joined: Fri Jan 15, 2010 12:33 amFollowed by: 2 members; Thanked: 47 times

by kstv » Wed Mar 31, 2010 5:49 am

How about n, 2n , 3n , 1 as options

I find this part confusing - If the probability of randomly drawing n balls of same color from the bag is 1/6
will it hold true for all values of n , should it not be 1/6^n

sanju09: GMAT Instructor; Posts: 3650; Joined: Wed Jan 21, 2009 4:27 amFollowed by: 80 members; Location: India; Thanked: 267 times; GMAT Score:760

by sanju09 » Wed Mar 31, 2010 5:59 am

kstv wrote:How about n, 2n , 3n , 1 as options

I find this part confusing - If the probability of randomly drawing n balls of same color from the bag is 1/6
will it hold true for all values of n , should it not be 1/6^n

I'm not sure how those options would work. I am looking for numbers to fill the options.

No, it's not true for all values of n, it's true for some very specific positive integers that form some sequence when arranged.

The mind is everything. What you think you become. –Lord Buddha

Sanjeev K Saxena
Quantitative Instructor
The Princeton Review - Manya Abroad
Lucknow-226001

www.manyagroup.com

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