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

Redeem

Good Number Properties Problem from GMAC paper test

This topic has expert replies
Post new topic Post Reply
Previous Topic Next Topic
Master | Next Rank: 500 Posts
Posts: 158
Joined: Mon Nov 02, 2009 5:49 pm
Thanked: 2 times
Followed by:3 members

Good Number Properties Problem from GMAC paper test

by tonebeeze » Mon May 16, 2011 2:43 pm
Can someone walk me through this one. thanks


If x, y, and z are positive integers and 3x = 4y = 7z, then the least possible value of x + y + z is

a. 33
b. 40
c. 49
d. 61
e. 84

OA = D
Our collective understanding of the GMAT grows through research, contribution, and teamwork. If you found a problem or comment challenging, helpful, or encouraging, please consider hitting the THANKS button!
Top
Source: — Problem Solving |
User avatar
Master | Next Rank: 500 Posts
Posts: 243
Joined: Sun Jul 12, 2009 7:12 am
Location: Dominican Republic
Thanked: 31 times
Followed by:2 members
GMAT Score:480

by MAAJ » Mon May 16, 2011 3:23 pm
Prime Factors
3 -> 3
4 -> 2,2
7 -> 7
LCM = 2x2x3x7 = 84

3x/84 = 4y/84 = 7z/84
x/28 = y/21 = z/12

If we make x, y and z equal to 1:
x = 28; y = 21; z = 12 and (x + y + z) = 28 + 21 + 12 = 61

That's how I got [spoiler] D? [/spoiler]

tonebeeze wrote:Can someone walk me through this one. thanks


If x, y, and z are positive integers and 3x = 4y = 7z, then the least possible value of x + y + z is

a. 33
b. 40
c. 49
d. 61
e. 84

OA = D
"There's a difference between interest and commitment. When you're interested in doing something, you do it only when circumstance permit. When you're committed to something, you accept no excuses, only results."
Top

GMAT/MBA Expert

User avatar
GMAT Instructor
Posts: 3835
Joined: Fri Apr 02, 2010 10:00 pm
Location: Milpitas, CA
Thanked: 1854 times
Followed by:523 members
GMAT Score:770

by Anurag@Gurome » Mon May 16, 2011 7:53 pm
tonebeeze wrote:Can someone walk me through this one. thanks


If x, y, and z are positive integers and 3x = 4y = 7z, then the least possible value of x + y + z is

a. 33
b. 40
c. 49
d. 61
e. 84

OA = D
Let 3x = 4y = 7z = k.
Or x = k/3,
y = k/4, and z = k/7.
Or, x+y+z = k/3 + k/4 + k/7 = (28k+21k+12k)/84 = 61k/84.
So, the least value of x+y+z is obtained at the least value of k.
Note that since k is a common multiple of 3, 4, and 7, its least value is the LCM of 3, 4, and 7 which is 84.
So, least value of x+y+z = 61.

The correct answer is d.
Anurag Mairal, Ph.D., MBA
GMAT Expert, Admissions and Career Guidance
Gurome, Inc.
1-800-566-4043 (USA)

Join Our Facebook Groups
GMAT with Gurome
https://www.facebook.com/groups/272466352793633/
Admissions with Gurome
https://www.facebook.com/groups/461459690536574/
Career Advising with Gurome
https://www.facebook.com/groups/360435787349781/
Top
Post new topic Post Reply
• Page 1 of 1