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.
Jul 1311:00 AM EDT
-12:30 PM EDT
Looking for your GMAT motivation to break through the score plateau? Pragati improved her score by massive 160 points with strategic guidance and hard-work! Find out how personalized mentorship and a strong mindset can turn GMAT struggles into success.
Jul 0901:00 PM EDT
-02:00 PM EDT
More Target Test Prep students are earning 100th percentile GMAT scores. Don’t settle for less when the Target Test Prep course gives you everything you need to score high on the GMAT. Start your 5-day free trial today.
Jul 1206:30 AM PDT
-08:30 AM PDT
Join our webinar to master GMAT RC Main Point Questions! Learn effective strategies to decipher passage themes and purposes. Senior Verbal Expert- Sunita Singhvi will equip you with tools to navigate complexities and avoid common traps set by the GMAT.
Jul 1508:00 PM PDT
-09:00 PM PDT
Full-length FE mock with insightful analytics, weakness diagnosis, and video explanations!
Jul 1611:00 AM EDT
-12:00 PM EDT
Prefer video-based learning? The Target Test Prep OnDemand course is a one-of-a-kind video masterclass featuring 400 hours of lecture-style teaching by Scott Woodbury-Stewart, founder of Target Test Prep and one of the most accomplished GMAT instructors.
Jul 1911:00 AM IST
-01:00 PM IST
Do RC/MSR passages scare you? e-GMAT is conducting a masterclass to help you learn – Learn effective reading strategies Tackle difficult RC & MSR with confidence Excel in timed test environment
16 Sep 2014, 01:08
Kudos
Bookmarks
A
Be sure to select an answer first to save it in the Error Log before revealing the correct answer (OA)!
Difficulty:
65%
(hard)
Question Stats:
53% (01:52) correct
47%
(01:58)
wrong
based on 132
sessions
History
Date
Time
Result
Not Attempted Yet
If \(x\) and \(y\) are positive integers, is \(10^x - y\) divisible by 9 ?
(1) \(y\) is divisible by 3
(2) \(10^x + y\) is not divisible by 9
(1) \(y\) is divisible by 3
(2) \(10^x + y\) is not divisible by 9
16 Sep 2014, 01:08
Kudos
Bookmarks
Official Solution:
If \(x\) and \(y\) are positive integers, is \(10^x - y\) divisible by 9 ?
Note that for any positive integer \(x\), \(10^x\) will have a digit sum equal to 1, so it will not be divisible by 3.
(1) \(y\) is divisible by 3.
In this case, \(10^x - y\) = (something not divisible by 3) - (something divisible by 3) = (something not divisible by 3). Since \(10^x - y\) is not divisible by 3, it is also not divisible by 9. Sufficient.
(2) \(10^x + y\) is not divisible by 9.
If \(y = 1\), the digit sum of \(10^x + y\) will be 2, so it won't be divisible by 9, but \(10^x - y\) will have only 9s as its digits, so it will be divisible by 9. However, if \(y = 2\), the digit sum of \(10^x + y\) will be 3, so it won't be divisible by 9, but \(10^x - y\) will have some number of 9s followed by an 8, so it won't be divisible by 9 either. Not sufficient.
Answer: A
If \(x\) and \(y\) are positive integers, is \(10^x - y\) divisible by 9 ?
Note that for any positive integer \(x\), \(10^x\) will have a digit sum equal to 1, so it will not be divisible by 3.
(1) \(y\) is divisible by 3.
In this case, \(10^x - y\) = (something not divisible by 3) - (something divisible by 3) = (something not divisible by 3). Since \(10^x - y\) is not divisible by 3, it is also not divisible by 9. Sufficient.
(2) \(10^x + y\) is not divisible by 9.
If \(y = 1\), the digit sum of \(10^x + y\) will be 2, so it won't be divisible by 9, but \(10^x - y\) will have only 9s as its digits, so it will be divisible by 9. However, if \(y = 2\), the digit sum of \(10^x + y\) will be 3, so it won't be divisible by 9, but \(10^x - y\) will have some number of 9s followed by an 8, so it won't be divisible by 9 either. Not sufficient.
Answer: A
23 May 2017, 06:21
Kudos
Bookmarks
Dear Sir,
I am having a doubt which might sound silly. Hence my apologies.
From the question, i understand is ((10^x)-y)/9?
Is it okay if I re-write this way: (10^x/9)-y/9 since they will have comment denominator?
Is that case, since x and y are positive, wouldn't the stem of the question itself denotes that it is not divisible by 9?
I am having a doubt which might sound silly. Hence my apologies.
From the question, i understand is ((10^x)-y)/9?
Is it okay if I re-write this way: (10^x/9)-y/9 since they will have comment denominator?
Is that case, since x and y are positive, wouldn't the stem of the question itself denotes that it is not divisible by 9?
