Author 
Message 
TAGS:

Hide Tags

Math Expert
Joined: 02 Sep 2009
Posts: 47101

Question Stats:
55% (01:11) correct 45% (01:05) wrong based on 164 sessions
HideShow timer Statistics



Math Expert
Joined: 02 Sep 2009
Posts: 47101

Re M2008 [#permalink]
Show Tags
16 Sep 2014, 01:08



Intern
Joined: 15 Nov 2015
Posts: 2

Re: M2008 [#permalink]
Show Tags
28 Mar 2016, 21:46
How is statement 1 sufficient?
If we pick numbers for statement 1 we can get two different answers. if x=2 and y=3, then 1003=97, Answer NO if x=2 and y=9, then 1009=81, Answer YES
Am I missing something?



Math Expert
Joined: 02 Sep 2009
Posts: 47101

Re: M2008 [#permalink]
Show Tags
28 Mar 2016, 22:16



Intern
Joined: 10 May 2017
Posts: 27

Re: M2008 [#permalink]
Show Tags
23 May 2017, 06:21
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 rewrite 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?



Math Expert
Joined: 02 Sep 2009
Posts: 47101

Re: M2008 [#permalink]
Show Tags
23 May 2017, 06:34
Manoraaju wrote: 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 rewrite 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? Yes, you can rewrite \(\frac{10^xy}{9}\) as \(\frac{10^x}{9}\frac{y}{9}\). But how can you say that \(\frac{10^x}{9}\frac{y}{9}\) will not be an integer? For example, if x = 1 and y = 1, then \(\frac{10^x}{9}\frac{y}{9}=1\)
_________________
New to the Math Forum? Please read this: Ultimate GMAT Quantitative Megathread  All You Need for Quant  PLEASE READ AND FOLLOW: 12 Rules for Posting!!! Resources: GMAT Math Book  Triangles  Polygons  Coordinate Geometry  Factorials  Circles  Number Theory  Remainders; 8. Overlapping Sets  PDF of Math Book; 10. Remainders  GMAT Prep Software Analysis  SEVEN SAMURAI OF 2012 (BEST DISCUSSIONS)  Tricky questions from previous years.
Collection of Questions: PS: 1. Tough and Tricky questions; 2. Hard questions; 3. Hard questions part 2; 4. Standard deviation; 5. Tough Problem Solving Questions With Solutions; 6. Probability and Combinations Questions With Solutions; 7 Tough and tricky exponents and roots questions; 8 12 Easy Pieces (or not?); 9 Bakers' Dozen; 10 Algebra set. ,11 Mixed Questions, 12 Fresh Meat DS: 1. DS tough questions; 2. DS tough questions part 2; 3. DS tough questions part 3; 4. DS Standard deviation; 5. Inequalities; 6. 700+ GMAT Data Sufficiency Questions With Explanations; 7 Tough and tricky exponents and roots questions; 8 The Discreet Charm of the DS; 9 Devil's Dozen!!!; 10 Number Properties set., 11 New DS set.
What are GMAT Club Tests? Extrahard Quant Tests with Brilliant Analytics



Manager
Joined: 16 Jan 2011
Posts: 102

Re: M2008 [#permalink]
Show Tags
04 Sep 2017, 08:30
Does this rule hold true for any integer? Quote: (something not divisible by 3)  (something divisible by 3) = (something not divisible by 3)



Math Expert
Joined: 02 Sep 2009
Posts: 47101

Re: M2008 [#permalink]
Show Tags
04 Sep 2017, 08:49
Galiya wrote: Does this rule hold true for any integer? Quote: (something not divisible by 3)  (something divisible by 3) = (something not divisible by 3) Yes. WHEN THE SUM OR THE DIFFERENCE OF NUMBERS IS A MULTIPLE OF AN INTEGER1. If integers \(a\) and \(b\) are both multiples of some integer \(k>1\) (divisible by \(k\)), then their sum and difference will also be a multiple of \(k\) (divisible by \(k\)):Example: \(a=6\) and \(b=9\), both divisible by 3 > \(a+b=15\) and \(ab=3\), again both divisible by 3. 2. If out of integers \(a\) and \(b\) one is a multiple of some integer \(k>1\) and another is not, then their sum and difference will NOT be a multiple of \(k\) (divisible by \(k\)):Example: \(a=6\), divisible by 3 and \(b=5\), not divisible by 3 > \(a+b=11\) and \(ab=1\), neither is divisible by 3. 3. If integers \(a\) and \(b\) both are NOT multiples of some integer \(k>1\) (divisible by \(k\)), then their sum and difference may or may not be a multiple of \(k\) (divisible by \(k\)):Example: \(a=5\) and \(b=4\), neither is divisible by 3 > \(a+b=9\), is divisible by 3 and \(ab=1\), is not divisible by 3; OR: \(a=6\) and \(b=3\), neither is divisible by 5 > \(a+b=9\) and \(ab=3\), neither is divisible by 5; OR: \(a=2\) and \(b=2\), neither is divisible by 4 > \(a+b=4\) and \(ab=0\), both are divisible by 4. For more on this check: 5. Divisibility/Multiples/Factors 6. Remainders For other subjects: ALL YOU NEED FOR QUANT ! ! !Ultimate GMAT Quantitative Megathread
_________________
New to the Math Forum? Please read this: Ultimate GMAT Quantitative Megathread  All You Need for Quant  PLEASE READ AND FOLLOW: 12 Rules for Posting!!! Resources: GMAT Math Book  Triangles  Polygons  Coordinate Geometry  Factorials  Circles  Number Theory  Remainders; 8. Overlapping Sets  PDF of Math Book; 10. Remainders  GMAT Prep Software Analysis  SEVEN SAMURAI OF 2012 (BEST DISCUSSIONS)  Tricky questions from previous years.
Collection of Questions: PS: 1. Tough and Tricky questions; 2. Hard questions; 3. Hard questions part 2; 4. Standard deviation; 5. Tough Problem Solving Questions With Solutions; 6. Probability and Combinations Questions With Solutions; 7 Tough and tricky exponents and roots questions; 8 12 Easy Pieces (or not?); 9 Bakers' Dozen; 10 Algebra set. ,11 Mixed Questions, 12 Fresh Meat DS: 1. DS tough questions; 2. DS tough questions part 2; 3. DS tough questions part 3; 4. DS Standard deviation; 5. Inequalities; 6. 700+ GMAT Data Sufficiency Questions With Explanations; 7 Tough and tricky exponents and roots questions; 8 The Discreet Charm of the DS; 9 Devil's Dozen!!!; 10 Number Properties set., 11 New DS set.
What are GMAT Club Tests? Extrahard Quant Tests with Brilliant Analytics



Intern
Joined: 04 Sep 2017
Posts: 1

Re: M2008 [#permalink]
Show Tags
04 Sep 2017, 08:59
Galiya wrote: Does this rule hold true for any integer? Quote: (something not divisible by 3)  (something divisible by 3) = (something not divisible by 3) Yeah this always holds true! Sent from my iPhone using GMAT Club Forum mobile app



Intern
Joined: 28 Mar 2017
Posts: 4

I am struggling a bit to understand option B. How are we approaching it?
Statement (2) by itself is insufficient. If \(y = 1\), the answer is "yes"; if \(y = 2\), the answer is "no".



Math Expert
Joined: 02 Sep 2009
Posts: 47101

Re: M2008 [#permalink]
Show Tags
22 Sep 2017, 07:25
Shiprasingh1100 wrote: I am struggling a bit to understand option B. How are we approaching it?
Statement (2) by itself is insufficient. If \(y = 1\), the answer is "yes"; if \(y = 2\), the answer is "no". If y = 1, then 10^x + 1 could be 11, 101, 1001, ... so as given in the second statement, not divisible by 9. In this case, 10^x  1 will be 9, 99, 999, ... so divisible by 9. Answer YES. If y = 2, then 10^x + 1 could be 12, 102, 1002, ... so as given in the second statement, not divisible by 9. In this case, 10^x  1 will be 8, 98, 998, ... so NOT divisible by 9. Answer NO.
_________________
New to the Math Forum? Please read this: Ultimate GMAT Quantitative Megathread  All You Need for Quant  PLEASE READ AND FOLLOW: 12 Rules for Posting!!! Resources: GMAT Math Book  Triangles  Polygons  Coordinate Geometry  Factorials  Circles  Number Theory  Remainders; 8. Overlapping Sets  PDF of Math Book; 10. Remainders  GMAT Prep Software Analysis  SEVEN SAMURAI OF 2012 (BEST DISCUSSIONS)  Tricky questions from previous years.
Collection of Questions: PS: 1. Tough and Tricky questions; 2. Hard questions; 3. Hard questions part 2; 4. Standard deviation; 5. Tough Problem Solving Questions With Solutions; 6. Probability and Combinations Questions With Solutions; 7 Tough and tricky exponents and roots questions; 8 12 Easy Pieces (or not?); 9 Bakers' Dozen; 10 Algebra set. ,11 Mixed Questions, 12 Fresh Meat DS: 1. DS tough questions; 2. DS tough questions part 2; 3. DS tough questions part 3; 4. DS Standard deviation; 5. Inequalities; 6. 700+ GMAT Data Sufficiency Questions With Explanations; 7 Tough and tricky exponents and roots questions; 8 The Discreet Charm of the DS; 9 Devil's Dozen!!!; 10 Number Properties set., 11 New DS set.
What are GMAT Club Tests? Extrahard Quant Tests with Brilliant Analytics



Intern
Status: Don't watch the clock,Do what it does, Keep Going.
Joined: 10 Jan 2017
Posts: 44

Re: M2008 [#permalink]
Show Tags
22 Sep 2017, 09:22
Shiprasingh1100 It is stated in the question that x is positive integer i.e. x can be 1,2,3,4,5,6, and so on .So, 10^x will have have respective value 10,100,1000 and so on. Thus in 2. when y=1 9,99,999, and so on will always be divisible by 9 whereas when y=2 it will not always be divisible by 9. Hope you get it . Kudos if you like my reply



Manager
Joined: 21 Jul 2017
Posts: 138
Location: India
Concentration: Social Entrepreneurship, Leadership
GPA: 4
WE: Project Management (Education)

Re: M2008 [#permalink]
Show Tags
22 Sep 2017, 20:00
Shiprasingh1100 wrote: I am struggling a bit to understand option B. How are we approaching it?
Statement (2) by itself is insufficient. If \(y = 1\), the answer is "yes"; if \(y = 2\), the answer is "no". The question is asking if 10^xy is divisible by 9. Since, for x=y=1; The answer is Yes and for x=2, y=9; The answer is No. Hence the option is not by itself sufficient.



Manager
Joined: 04 Jul 2017
Posts: 60
Location: India
Concentration: Marketing, General Management
Schools: HBS '20, Stanford '20, Wharton '20, Sloan '20, CBS '20, Tuck '20, Yale '20, Johnson '20, INSEAD Jan '19, Insead Sept'18, ISB '19
GPA: 1
WE: Analyst (Consulting)

Re: M2008 [#permalink]
Show Tags
25 Sep 2017, 10:39
oirfan wrote: How is statement 1 sufficient?
If we pick numbers for statement 1 we can get two different answers. if x=2 and y=3, then 1003=97, Answer NO if x=2 and y=9, then 1009=81, Answer YES
Am I missing something? Even I make such mistakes, be careful. How should one avoid such mistakes?










