Forum Home > GMAT > Quantitative > Problem Solving (PS)
Events & Promotions
|
|
GMAT Club Daily Prep
Thank you for using the timer - this advanced tool can estimate your performance and suggest more practice questions. We have subscribed you to Daily Prep Questions via email.
Customized
for You
Track
Your Progress
Practice
Pays
Not interested in getting valuable practice questions and articles delivered to your email? No problem, unsubscribe here.
Dec 1310:00 AM EST
-12:00 PM EST
Have you ever wondered how to score a PERFECT 805 on the GMAT? Meet Julia, a banking professional who used the Target Test Prep course to achieve this incredible feat. Julia's story is nothing short of an inspiration.
Dec 1410:00 AM EST
-12:00 PM EST
Think a 100% GMAT Verbal score is out of your reach? Target Test Prep will make you think again! Our course uses techniques such as topical study and spaced repetition to maximize knowledge retention and make studying simple and fun.
Dec 1411:00 AM IST
-01:00 PM IST
Attend this session to learn how to Deconstruct arguments, Pre-Think Author’s Assumptions, and apply Negation Test.- Dec 15
11:00 AM IST
-01:00 PM IST
Attend this free GMAT Algebra Webinar and learn how to master the most challenging Inequalities and Absolute Value problems with ease. 
Dec 1608:00 AM PST
-11:59 PM PST
GMAT Club 12 Days of Christmas is a 4th Annual GMAT Club Winter Competition based on solving questions. This is the Winter GMAT competition on GMAT Club with an amazing opportunity to win over $40,000 worth of prizes!
12 Apr 2017, 13:22
Kudos
Bookmarks
B
Be sure to select an answer first to save it in the Error Log before revealing the correct answer (OA)!
Difficulty:
5%
(low)
Question Stats:
84% (01:04) correct
16%
(01:57)
wrong
based on 191
sessions
History
Date
Time
Result
Not Attempted Yet
If xy = 10, what is the value of x + y?
1. x and y are positive numbers.
2. 1/x + 1/y = 3
1. x and y are positive numbers.
2. 1/x + 1/y = 3
Source: McGraw Hill's GMAT
12 Apr 2017, 13:37
Kudos
Bookmarks
1. x and y are positive numbers.
The statement is vague and x and y can take any values (fractions, integers), hence this statement is not sufficient.
2. 1/x + 1/y = 3
Above statement can be written as
(x+y)/xy = 3
Substituting value for xy above
(x+y)/10 = 3
x+y = 30
This statement is sufficient.
Answer is B.
The statement is vague and x and y can take any values (fractions, integers), hence this statement is not sufficient.
2. 1/x + 1/y = 3
Above statement can be written as
(x+y)/xy = 3
Substituting value for xy above
(x+y)/10 = 3
x+y = 30
This statement is sufficient.
Answer is B.
12 Apr 2017, 13:39
Kudos
Bookmarks
SajjadAhmad
Source: McGraw Hill GMAT
If xy = 10, what is the value of x + y?
1. x and y are positive numbers.
2. 1/x + 1/y = 3
If xy = 10, what is the value of x + y?
1. x and y are positive numbers.
2. 1/x + 1/y = 3
Target question: What is the value of x + y?
Given: xy = 10
Statement 1: x and y are positive numbers.
This statement doesn't feel sufficient, so I'll TEST some values.
There are several values of x and y that satisfy statement 1 and the given information. Here are two:
Case a: x = 1 and y = 10, in which case x + y = 1 + 10 = 11
Case b: x = 2 and y = 5, in which case x + y = 2 + 5 = 7
Since we cannot answer the target question with certainty, statement 1 is NOT SUFFICIENT
Statement 2: 1/x + 1/y = 3
Let's combine these fractions. To do so, we'll need a common denominator.
A common denominator of x and y is xy.
So, 1/x = y/xy and 1/y = x/xy
We can now take: 1/x + 1/y = 3
And rewrite it as: y/xy + x/xy = 3
Combine the fractions: (y + x)/xy = 3
Use the given information to get: (y + x)/10 = 3
Multiply both sides by 10 to get: y + x = 30
PERFECT!
Since we can answer the target question with certainty, statement 2 is SUFFICIENT
Answer:
Cheers,
Brent
