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.
Apr 1612:00 PM EDT
-11:59 PM EDT
You’re first to know: Save $200 on GMAT prep starting tomorrow, 4/13. Get 6 official practice tests and study with real questions. Be ready to save!
Apr 2610:00 AM EDT
-11:00 AM EDT
The Target Test Prep course represents a quantum leap forward in GMAT preparation, a radical reinterpretation of the way that students should study. Try before you buy with a 5-day, full-access trial of the course for FREE!
Apr 2711:00 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
Apr 2808:00 AM PDT
-11:00 AM PDT
Whether you are just beginning your MBA journey or fine-tuning your path to a 700+ score, GMAT Day is designed to give you a competitive edge.
D
Be sure to select an answer first to save it in the Error Log before revealing the correct answer (OA)!
Difficulty:
75%
(hard)
Question Stats:
59% (03:03) correct
41%
(02:31)
wrong
based on 29
sessions
History
Date
Time
Result
Not Attempted Yet
A sequence of numbers is such that a1 = 11, a2 =16, and each subsequent an = an-2 + 9. Which of the following numbers is a member of the sequence?
A) 216
B) 246
C) 289
D) 299
E) 368
A) 216
B) 246
C) 289
D) 299
E) 368
Archived Topic
Hi there,
This topic has been closed and archived due to inactivity or violation of community quality standards. No more replies are possible here.
Where to now? Join ongoing discussions on thousands of quality questions in our Problem Solving (PS) Forum
Still interested in this question? Check out the "Best Topics" block below for a better discussion on this exact question, as well as several more related questions.
Thank you for understanding, and happy exploring!
30 Aug 2012, 20:49
Kudos
Bookmarks
A sequence of numbers is such that a1 = 11, a2 =16, and each subsequent an = an-2 + 9. Which of the following numbers is a member of the sequence?
A) 216
B) 246
C) 289
D) 299
E) 368
Two ways of solving this
First Approach
each odd term(1st , 3rd, 5th,...) of the sequence is given by 11 + 9*(something)
each even term(2nd, 4th, 6th...) of the sequence is given by 16 + 9*(something)
So if you subtract the numbers by 11 or 16 then it should be divisible by 9
216-11(=205) or 216-16(=200) are not divisible by 9
246-11(=235) or 246-16(=240) are not divisible by 9
289-11(=278) or 289-16(=273) are not divisible by 9
299-11(=288) is divisible by 9 ANSWER, 299-16(=283) are not divisible by 9
368-11(=357) or 368-16(=352) are not divisible by 9
So, Answer is D
Second Approach
Numbers in the series are 11 + 9*(something) or 16 + 9*(something)
Since 4 number are between 200-300 so lets try finding out the values in the series between 200-300
11 + 9*21 = 200
16 + 9*21 = 206
So numbers in the sequence will be
200,211,222,233,244,255,266,277,288,299
206,222,238,254,270,286,302
Since 299 is the answer choice so answer is D
If we did not get any number out of options A to D to be in the sequence than answer will be E
Hope it helps!
A) 216
B) 246
C) 289
D) 299
E) 368
Two ways of solving this
First Approach
each odd term(1st , 3rd, 5th,...) of the sequence is given by 11 + 9*(something)
each even term(2nd, 4th, 6th...) of the sequence is given by 16 + 9*(something)
So if you subtract the numbers by 11 or 16 then it should be divisible by 9
216-11(=205) or 216-16(=200) are not divisible by 9
246-11(=235) or 246-16(=240) are not divisible by 9
289-11(=278) or 289-16(=273) are not divisible by 9
299-11(=288) is divisible by 9 ANSWER, 299-16(=283) are not divisible by 9
368-11(=357) or 368-16(=352) are not divisible by 9
So, Answer is D
Second Approach
Numbers in the series are 11 + 9*(something) or 16 + 9*(something)
Since 4 number are between 200-300 so lets try finding out the values in the series between 200-300
11 + 9*21 = 200
16 + 9*21 = 206
So numbers in the sequence will be
200,211,222,233,244,255,266,277,288,299
206,222,238,254,270,286,302
Since 299 is the answer choice so answer is D
If we did not get any number out of options A to D to be in the sequence than answer will be E
Hope it helps!
30 Aug 2012, 23:07
Kudos
Bookmarks
Babzsn84
The question takes less than a minute if you understand divisibility well. You might want to check out these posts first:
https://www.gmatclub.com/forum/veritas-prep-resource-links-no-longer-available-399979.html#/2011/04 ... unraveled/
https://www.gmatclub.com/forum/veritas-prep-resource-links-no-longer-available-399979.html#/2011/04 ... y-applied/
Each term of the sequence is of the form (11 + 9n) or (16 + 9m) (n and m are non negative integers)
Note that 11+9n is same as 9a + 2 and 16+9m is same as 9b + 7. Go through the divisibility post if you are not sure why.
Sequence will look like this: 11, 16, 20, 25, 29, 34 etc
From the given options, you have to find the option which is of one of the two forms: (9a + 2) or (9a + 7)
How do you do that? Use divisibility rule of 9.
216 - Since 2+1+6 = 9, this number is divisible by 9 and hence is of the form 9a.
246 - Since 2+4+6 = 12, this number will give remainder 3 when divided by 9. It is of the form 9a + 3
289 - By same logic, it gives remainder 1 when divided by 9 and is of them form 9a + 1
299 - It gives remainder 2 when divided by 9 and is of the form 9a + 2
This is the required option.
The fun thing about this question is that it seems to be testing sequences but actually it is testing your understanding of divisibility. This is true for many GMAT questions. They test the basic concepts but you have to work to figure out the particular concept they are testing.
