Author 
Message 
TAGS:

Hide Tags

Math Expert
Joined: 02 Sep 2009
Posts: 49206

Question Stats:
40% (01:02) correct 60% (01:09) wrong based on 149 sessions
HideShow timer Statistics



Math Expert
Joined: 02 Sep 2009
Posts: 49206

Re M0917
[#permalink]
Show Tags
16 Sep 2014, 00:39



Intern
Joined: 22 Oct 2014
Posts: 4
GPA: 4
WE: Marketing (Manufacturing)

Re: M0917
[#permalink]
Show Tags
19 Dec 2014, 00:18
I think that the answer is wrong. The question is asking on how many pages does number 9 appear and not how many times does number 9 appear. Therefore page 99 has to be counted once. Hence correct answer is 18x7= 126



Math Expert
Joined: 02 Sep 2009
Posts: 49206

Re: M0917
[#permalink]
Show Tags
19 Dec 2014, 08:28
alemazza wrote: I think that the answer is wrong. The question is asking on how many pages does number 9 appear and not how many times does number 9 appear. Therefore page 99 has to be counted once. Hence correct answer is 18x7= 126 That's not correct. Pages with 9 in 100: 9, 19, 29, 39, 49, 59, 69, 79, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, and 99. Total of 19 pages. 19*7 = 133.
_________________
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: 24 Jun 2015
Posts: 46

Re: M0917
[#permalink]
Show Tags
01 Jul 2015, 08:28
Hi,
If I would like to solve with combinatorics, may be slot method _ x _ x _ ... How the method would proceed?
Thanks a lot.
Best regards.
Luis Navarro Looking for 700



Manager
Joined: 24 Oct 2013
Posts: 145
Location: India
Concentration: General Management, Strategy
WE: Information Technology (Computer Software)

Re: M0917
[#permalink]
Show Tags
14 Mar 2016, 07:09
Here are the list of numbers 9, 19, 29, 39, 49, 59, 69, 79, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, and 99 Total  20 9's in 1 hundred. Total = 20*7 = 140



Math Expert
Joined: 02 Aug 2009
Posts: 6785

Re: M0917
[#permalink]
Show Tags
14 Mar 2016, 07:15
deepthit wrote: Here are the list of numbers 9, 19, 29, 39, 49, 59, 69, 79, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, and 99 Total  20 9's in 1 hundred. Total = 20*7 = 140 the Q ask us about the PAGES on which 9 occurs, so 99 will be ONE and not two separately so 19*7
_________________
1) Absolute modulus : http://gmatclub.com/forum/absolutemodulusabetterunderstanding210849.html#p1622372 2)Combination of similar and dissimilar things : http://gmatclub.com/forum/topic215915.html 3) effects of arithmetic operations : https://gmatclub.com/forum/effectsofarithmeticoperationsonfractions269413.html
GMAT online Tutor



Intern
Joined: 16 Feb 2015
Posts: 3

Re: M0917
[#permalink]
Show Tags
06 Jul 2016, 05:17
Another approach:
Pages from 1 to 705.
9 as units digit: 9 first number in set, 699last number in set, set is inclusive. Distance between each occurrence of '9' in units digits = 10. >> Number of occurrences = [(6999)/10] + 1 = 70
9 as tenths digit: if hundredth digit is '0', we have 90first number in set, 98last number in set (omit 99 as already counted above), set is inclusive. >> Number of occurrences: (9890) + 1 = 9 Possible hundredth digits: 0 1 2 3 4 5 6 >> total number of occurrences = 9*7=63
Finally: total pages with '9' = 63 +70 = 133



Senior Manager
Joined: 31 Mar 2016
Posts: 396
Location: India
Concentration: Operations, Finance
GPA: 3.8
WE: Operations (Commercial Banking)

Re M0917
[#permalink]
Show Tags
29 Jul 2016, 10:47
I think this is a highquality question and the explanation isn't clear enough, please elaborate. Hi Bunuel,
Can you please take time to explain how this can be done using combination / permutations ?



Manager
Joined: 17 Aug 2015
Posts: 113

Re: M0917
[#permalink]
Show Tags
02 Sep 2016, 10:20
99 NEEDS to be counted as one page as question asks the number of pages on which 9 appears not the total number of 9's



Intern
Joined: 26 May 2016
Posts: 22

Re: M0917
[#permalink]
Show Tags
02 May 2017, 04:25
For those who want to solve this using combinatorics
>> !!!
You do not have the required permissions to view the files attached to this post.










