Percentage Problem

This topic has expert replies
Master | Next Rank: 500 Posts
Posts: 190
Joined: Thu Jan 14, 2010 8:29 pm
Thanked: 2 times

Percentage Problem

by phoenix9801 » Sun May 20, 2012 8:54 am
1-
The negative integer x and the positive integer y are related by the inequality x² > y. Which of the following could be greater than zero?
a) xy
b) x+y
c) x-y
d) x-y^2
e) y-x^2


3-
If 7(x + 1) = 8(y − 1), and x and y are both positive integers, what is the least possible value of x + y?
a) 1
b) 2
c) 7
d) 9
e) 15
Last edited by phoenix9801 on Sun May 20, 2012 6:04 pm, edited 1 time in total.
Source: — Problem Solving |

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 » Sun May 20, 2012 9:05 am
1- The negative integer x and the positive integer y are related by the inequality x² > y. Which of the following could be greater than zero?
a) xy
b) x+y
c) x-y
d) x-y^2
e) y-x^2
x = negative, y = positive such that x² > y or y - x² < 0
xy = (-ve)(+ve) = -ve < 0
x + y = (-ve) + (+ve) = may or may not be > 0
x - y = (-ve) - (+ve) = -ve < 0
x - y² = (-ve) - (+ve) = -ve < 0
y - x² < 0 (given)

The only possibility is B.
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/

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 » Sun May 20, 2012 5:56 pm
phoenix9801 wrote:1-

3-
If 7(x + 1) = 8(y − 1), and x and y are both positive integers, what is the least possible value of x + y?
a) 1
b) 2
c) 7
d) 9
e) 15
x + y cannot be 1 as x and y are both positive integers.
x + y cannot be 2, because then x = y = 1 but in that case 7(x + 1) is not equal to 8(y - 1)
Now x = 2, 3, 4, 5, 6 gives the value of 7(x + 1) as 21, 28, 35, 42, 49, which cannot be equal to 8(y - 1) for any integer value, as these values are not multiples of 8.

Next, if x = 7, y = 8, then 7(x + 1) = 7 * 8 = 56 and 8(y - 1) = 8 * 7 = 56
So, x + y = 15

The correct answer is E.
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/