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

Redeem

Fractions problem from OG 2nd Ed. Q42

This topic has expert replies
Post new topic Post Reply
Previous Topic Next Topic
Junior | Next Rank: 30 Posts
Posts: 11
Joined: Sat Jan 15, 2011 3:40 pm

Fractions problem from OG 2nd Ed. Q42

by quaktar0004 » Tue Feb 22, 2011 5:25 pm
42. If x>3000, then the value of x/2x + 1 is closest to

A. 1/6
B. 1/3
C. 10/21
D. 1/2
E. 3/2


My thinking was that the number 3000 didn't matter. So I made the 3000=3, and x=4.

4 4
___ _____
=
2(4) +1 9


4/9 is slightly less than half. I looked over the answer choices and thought that 10/21 (also slightly less than half) would be the closest. However, the correct answer is 1/2.

Where did I go wrong on this one?

Please advise.

Thank,
Top
Source: — Problem Solving |
User avatar
Legendary Member
Posts: 1255
Joined: Fri Nov 07, 2008 2:08 pm
Location: St. Louis
Thanked: 312 times
Followed by:90 members

by Tani » Tue Feb 22, 2011 5:30 pm
When you use a small value for X the +1 makes a huge difference. If x = 1, the value would be 1/3. However, when x is very large, the +1 has very little effect. 3000/6001 is very close to 1/2. 3,000,000/6,000,001 is even closer to 1/2.
Tani Wolff
Top
Legendary Member
Posts: 1337
Joined: Sat Dec 27, 2008 6:29 pm
Thanked: 127 times
Followed by:10 members

by Night reader » Tue Feb 22, 2011 5:44 pm
the notation should be precise :) x/(2x+1)
We take notice of two things that x is huge, x>3000 and our nominator and denominator values are different by rate of 2x plus 1, where 1 is not significant number. So if we cancel 1 in denominator we get x/2x OR 1/2

answer D
quaktar0004 wrote:42. If x>3000, then the value of x/2x + 1 is closest to

A. 1/6
B. 1/3
C. 10/21
D. 1/2
E. 3/2


My thinking was that the number 3000 didn't matter. So I made the 3000=3, and x=4.

4 4
___ _____
=
2(4) +1 9


4/9 is slightly less than half. I looked over the answer choices and thought that 10/21 (also slightly less than half) would be the closest. However, the correct answer is 1/2.

Where did I go wrong on this one?

Please advise.

Thank,
My knowledge frontiers came to evolve the GMATPill's methods - the credited study means to boost the Verbal competence. I really like their videos, especially for RC, CR and SC. You do check their study methods at https://www.gmatpill.com
Top
Post new topic Post Reply
• Page 1 of 1