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

Redeem

tree branches

This topic has expert replies
Post new topic Post Reply
Previous Topic Next Topic
Senior | Next Rank: 100 Posts
Posts: 69
Joined: Fri Mar 25, 2011 11:08 am
Thanked: 1 times

tree branches

by smodak » Fri Jun 24, 2011 11:29 am
Kim finds a 1-meter tree branch and marks it off in thirds and fifths. She then breaks the branch along all the markings and removes one piece of every distinct length. What fraction of the original branch remains?

A) 2/5
B) 7/15
C) 1/2
D) 8/15
E) 3/5

OA: E

Please explain your answer.
Top
Source: — Problem Solving |
Legendary Member
Posts: 1084
Joined: Fri Apr 15, 2011 2:33 pm
Thanked: 158 times
Followed by:21 members

by pemdas » Fri Jun 24, 2011 12:03 pm
you need to produce ascending array for all the markings:
1/3, 2/3, 1
1/5, 2/5, 3/5, 4/5, 1
________________________
multiply everything by 5 and 3 (alowing LCM 15):
5,10,15
3,6,9,12,15 ---> 3,5,6,9,10,12,15 (remember we have common denominator of 15)
_________________________
now we get pieces of distinct sizes (distance between markings)
{3,2,1,3,1,2,3) and we get all repeats in 3,2 and 1, So we subtract 6 and get (15-6)/15 or 3/5


smodak wrote:Kim finds a 1-meter tree branch and marks it off in thirds and fifths. She then breaks the branch along all the markings and removes one piece of every distinct length. What fraction of the original branch remains?

A) 2/5
B) 7/15
C) 1/2
D) 8/15
E) 3/5

OA: E

Please explain your answer.
Success doesn't come overnight!
Top
User avatar
GMAT Instructor
Posts: 15539
Joined: Tue May 25, 2010 12:04 pm
Location: New York, NY
Thanked: 13060 times
Followed by:1906 members
GMAT Score:790

by GMATGuruNY » Fri Jun 24, 2011 3:49 pm
smodak wrote:Kim finds a 1-meter tree branch and marks it off in thirds and fifths. She then breaks the branch along all the markings and removes one piece of every distinct length. What fraction of the original branch remains?

A) 2/5
B) 7/15
C) 1/2
D) 8/15
E) 3/5

OA: E

Please explain your answer.
Since the question asks for a fraction, the length of the branch can be any value.
Let branch = 15.
Divided into thirds and fifths, we get:
Image
Distinct lengths are 1, 2 and 3.
Total - distinct lengths = 15-1-2-3 = 9.
Remaining length/Total = 9/15 = 3/5.

The correct answer is E.
Private tutor exclusively for the GMAT and GRE, with over 20 years of experience.
Followed here and elsewhere by over 1900 test-takers.
I have worked with students based in the US, Australia, Taiwan, China, Tajikistan, Kuwait, Saudi Arabia -- a long list of countries.
My students have been admitted to HBS, CBS, Tuck, Yale, Stern, Fuqua -- a long list of top programs.

As a tutor, I don't simply teach you how I would approach problems.
I unlock the best way for YOU to solve problems.

For more information, please email me (Mitch Hunt) at [email protected].
Student Review #1
Student Review #2
Student Review #3
Top
Post new topic Post Reply
• Page 1 of 1