Probability - Columbus elementary school - The Beat The GMAT Forum

Probability - Columbus elementary school

Expert replies

GMAT/MBA Expert

Brent@GMATPrepNow: GMAT Instructor; Posts: 16207; Joined: Mon Dec 08, 2008 6:26 pmFollowed by: 1268 members; Location: Vancouver, BC; Thanked: 5254 times; GMAT Score:770

by Brent@GMATPrepNow » Sun Dec 28, 2008 11:10 am

If a child is randomly selected from Columbus elementary school, what is the probability that the child will be a boy?

(1) If 25 boys are removed from the school, the probability of selecting a boy will be 0.75
(2) There are 35 more boys than girls

Brent Hanneson - Creator of GMATPrepNow.com

Like this post

Source: Beat The GMAT — Data Sufficiency | Sun Dec 28, 2008 11:10 am

cramya: Legendary Member; Posts: 2467; Joined: Thu Aug 28, 2008 6:14 pmFollowed by: 11 members; Thanked: 331 times

by cramya » Sun Dec 28, 2008 11:15 am

Hope I dint fall in to the trap.

Is it C)?

x->boys
y->girls

Stmt I

x+75 = 3y

Stmt II

y = x-35

Together solve for x and y

(If I did fall in to the trap then its between A and C)

Like this post

GMAT/MBA Expert

Brent@GMATPrepNow: GMAT Instructor; Posts: 16207; Joined: Mon Dec 08, 2008 6:26 pmFollowed by: 1268 members; Location: Vancouver, BC; Thanked: 5254 times; GMAT Score:770

by Brent@GMATPrepNow » Sun Dec 28, 2008 12:42 pm

The answer is, indeed, C.
Nice work, cramya!

Brent Hanneson - Creator of GMATPrepNow.com

Like this post

cramya: Legendary Member; Posts: 2467; Joined: Thu Aug 28, 2008 6:14 pmFollowed by: 11 members; Thanked: 331 times

by cramya » Sun Dec 28, 2008 12:47 pm

Thanks to you for coming back after the christmas break and posting some good questions!

Wish u a happy new year!

Like this post

vittalgmat: Legendary Member; Posts: 621; Joined: Wed Apr 09, 2008 7:13 pmFollowed by: 4 members; Thanked: 33 times

by vittalgmat » Sun Dec 28, 2008 8:20 pm

Hi Cramya,
I am getting a different eqn in stmt 1.
here is my approach. let me know if something is wrong.

(B - 25) / (B -25 +G) = 3/4

-> 4B - 100 = 3B -75 +3G
-> 4B-3B = 100-75 +3G
-> B = 25 +3G
-> B -25 = 3G

However, this does not affect the final result.

Like this post

cramya: Legendary Member; Posts: 2467; Joined: Thu Aug 28, 2008 6:14 pmFollowed by: 11 members; Thanked: 331 times

by cramya » Sun Dec 28, 2008 8:23 pm

Vittal, Urs is correct. There should be a -25 in the numerator

Like this post

Post new topic Post Reply

• Page 1 of 1

GMAT Course Reviews

563 reviews

1168 reviews

431 reviews

359 reviews

147 reviews

5/5

5 Star (563 Reviews)

"Target Test Prep is the closest to the official version of the GMAT exam, about 99% accuracy in terms of the quality and quantity of information. The course has excellently created singular sets of focused lessons and tests for every possible topic that one could come across in the official GMAT exam."

"The TTP course maximizes the efficiency of the time you spend studying. It will take time and effort but I could almost guarantee that if you complete the course exactly as it is laid out you will get an amazing score. They also have a very responsive team willing to help with any questions you might have."

"TTP has two things that I think no other test prep company offers: A teaching approach that reinforces understanding and an attitude that will give you the mental preparedness needed to succeed on the test. TTP gives you a deep understanding of the concept you need to know while teaching you how to think."

Write a Review