Jul 20 07:00 AM PDT  09:00 AM PDT Attend this webinar and master GMAT SC in 10 days by learning how meaning and logic can help you tackle 700+ level SC questions with ease. Jul 21 07:00 AM PDT  09:00 AM PDT Attend this webinar to learn a structured approach to solve 700+ Number Properties question in less than 2 minutes Jul 26 08:00 AM PDT  09:00 AM PDT The Competition Continues  Game of Timers is a teambased competition based on solving GMAT questions to win epic prizes! Starting July 1st, compete to win prep materials while studying for GMAT! Registration is Open! Ends July 26th Jul 27 07:00 AM PDT  09:00 AM PDT Learn reading strategies that can help even nonvoracious reader to master GMAT RC
Author 
Message 
TAGS:

Hide Tags

Math Expert
Joined: 02 Sep 2009
Posts: 56300

Question Stats:
40% (02:12) correct 60% (01:40) wrong based on 130 sessions
HideShow timer Statistics
If in a sixdigit integer \(N\), \(F(k)\) is the value of the \(kth\) digit, is \(N\) divisible by 7 (For example, \(F(4)\) is the value of the hundreds digit of \(N\))? (1) \(F(1) = F(4), F(2) = F(5), F(3) = F(6)\) (2) \(F(1) = F(2) = ... = F(6)\)
Official Answer and Stats are available only to registered users. Register/ Login.
_________________



Math Expert
Joined: 02 Sep 2009
Posts: 56300

Re M1529
[#permalink]
Show Tags
16 Sep 2014, 00:56
Official Solution:Statements (1) and (2) by themselves are sufficient. S1 tells us that the last three digits of \(N\) are the same as the first three digits: \(N = abcabc\). Note that \(N = abc*1000 + abc = abc*1001\). As 1001 is divisible by 7, \(N\) is also divisible by 7. Answer: D
_________________



Intern
Joined: 14 Jan 2012
Posts: 9

Re: M1529
[#permalink]
Show Tags
26 Sep 2014, 12:39
and S2 sufficient because N=a*111111 where 111111 is divisible by 7? I haven't memorized divisibility rule for 7



Math Expert
Joined: 02 Sep 2009
Posts: 56300

Re: M1529
[#permalink]
Show Tags
29 Sep 2014, 06:03
Boycot wrote: and S2 sufficient because N=a*111111 where 111111 is divisible by 7? I haven't memorized divisibility rule for 7 You can find divisibility rules here: mathnumbertheory88376.html
_________________



Intern
Joined: 09 Dec 2013
Posts: 8

Re: M1529
[#permalink]
Show Tags
21 Oct 2014, 07:32
Quote: (For example, F(4) is the value of the hundreds digit of N)? Sorry if I am wrong, but I believe the example should be F(4) is the value of the thousands digit of N .



Math Expert
Joined: 02 Sep 2009
Posts: 56300

Re: M1529
[#permalink]
Show Tags
21 Oct 2014, 07:35
martinnotceoyet wrote: Quote: (For example, F(4) is the value of the hundreds digit of N)? Sorry if I am wrong, but I believe the example should be F(4) is the value of the thousands digit of N . 123,456 1  HUNDRED THOUSANDS 2  TEN THOUSANDS 3  THOUSANDS 4  HUNDREDS5  TENS 6  UNITS
_________________



Intern
Joined: 09 Dec 2013
Posts: 8

Re: M1529
[#permalink]
Show Tags
21 Oct 2014, 08:02
Omg, sure ! Thank you very much



Intern
Joined: 09 Aug 2014
Posts: 9

Re M1529
[#permalink]
Show Tags
19 Mar 2015, 05:18
I think this question is good and not helpful. Text seems confusing. F(k) is the value of the k−th digit. So F(4) means the value of the 4th digit which is thousands, right?



Math Expert
Joined: 02 Sep 2009
Posts: 56300

Re: M1529
[#permalink]
Show Tags
19 Mar 2015, 05:24
IonutCZ wrote: I think this question is good and not helpful. Text seems confusing. F(k) is the value of the k−th digit. So F(4) means the value of the 4th digit which is thousands, right? Please check here: m15184061.html#p1430861
_________________



Intern
Joined: 14 Feb 2013
Posts: 7

Re: M1529
[#permalink]
Show Tags
30 Mar 2015, 08:39
Dear Bunuel
Could you please tell me what's the reasoning behind Statement 2? Is it the abovediscussed fact with x*111'111? If that is indeed the case, how should one get that 111111 is divisible by 7 within the 2 mins given?:) Would be more than happy to get enlighted...
Thx vm, Dark Might



Intern
Joined: 15 Apr 2015
Posts: 8

Re M1529
[#permalink]
Show Tags
27 Aug 2015, 10:48
I think this the explanation isn't clear enough, please elaborate.



Intern
Joined: 17 Oct 2015
Posts: 17
Concentration: Technology, Leadership

Re M1529
[#permalink]
Show Tags
10 Feb 2016, 04:54
I think this is a highquality question and the explanation isn't clear enough, please elaborate. If someone could elaborate more... I just cant understand the reasons related at the explanations...



Current Student
Joined: 12 Aug 2015
Posts: 2609

mestrec wrote: I think this is a highquality question and the explanation isn't clear enough, please elaborate. If someone could elaborate more... I just cant understand the reasons related at the explanations... I agree with you... And More importantly i am not sure divisibility by 7 is really on the GMAT maybe mikemcgarry can shed some light on whether we really need to do such questions or not .. Regards chirag
_________________



Intern
Joined: 05 Nov 2012
Posts: 45

Re: M1529
[#permalink]
Show Tags
06 Apr 2016, 04:29
Bunuel wrote: Official Solution:
Statements (1) and (2) by themselves are sufficient. S1 tells us that the last three digits of \(N\) are the same as the first three digits: \(N = abcabc\). Note that \(N = abc*1000 + abc = abc*1001\). As 1001 is divisible by 7, \(N\) is also divisible by 7.
Answer: D Hi Bunuel, I am not sure if this part of the question is constructed properly. F(k) is the value of the k−th digit, (For example, F(4) is the value of the hundreds digit of N). Going by the statement you have given F (4) should be the value of the 4th digit right?. Also if I look at statement 1, F(1) = F(4) then here you have implied that the 1st digit = 4th digit. Therefore the question itself has clarity issues since how can F (K) stand for the kth digit as well as be the value for hundreds digit. Hope my question is clear.



Intern
Joined: 05 Nov 2012
Posts: 45

Re: M1529
[#permalink]
Show Tags
06 Apr 2016, 04:30
Bunuel wrote: Official Solution:
Statements (1) and (2) by themselves are sufficient. S1 tells us that the last three digits of \(N\) are the same as the first three digits: \(N = abcabc\). Note that \(N = abc*1000 + abc = abc*1001\). As 1001 is divisible by 7, \(N\) is also divisible by 7.
Answer: D Hi Bunuel, I am not sure if this part of the question is constructed properly. F(k) is the value of the k−th digit, (For example, F(4) is the value of the hundreds digit of N). Going by the statement you have given F (4) should be the value of the 4th digit right?. Also if I look at statement 1, F(1) = F(4) then here you have implied that the 1st digit = 4th digit. Therefore the question itself has clarity issues since how can F (K) stand for the kth digit as well as be the value for hundreds digit. Hope my question is clear.



Math Expert
Joined: 02 Aug 2009
Posts: 7764

Re: M1529
[#permalink]
Show Tags
06 Apr 2016, 05:19
nishatfarhat87 wrote: Bunuel wrote: Official Solution:
Statements (1) and (2) by themselves are sufficient. S1 tells us that the last three digits of \(N\) are the same as the first three digits: \(N = abcabc\). Note that \(N = abc*1000 + abc = abc*1001\). As 1001 is divisible by 7, \(N\) is also divisible by 7.
Answer: D Hi Bunuel, I am not sure if this part of the question is constructed properly. F(k) is the value of the k−th digit, (For example, F(4) is the value of the hundreds digit of N). Going by the statement you have given F (4) should be the value of the 4th digit right?. Also if I look at statement 1, F(1) = F(4) then here you have implied that the 1st digit = 4th digit. Therefore the question itself has clarity issues since how can F (K) stand for the kth digit as well as be the value for hundreds digit. Hope my question is clear. Hi .. why cant be two digits have same value .. example 123123.. here F(1) = F(4) = 1.. similarly other numbers can be seen as F(2) = F(5) = 2.. F(3) = F(6) = 3..
_________________



Senior Manager
Joined: 31 Mar 2016
Posts: 376
Location: India
Concentration: Operations, Finance
GPA: 3.8
WE: Operations (Commercial Banking)

Re M1529
[#permalink]
Show Tags
22 Aug 2016, 04:13
I think this is a highquality question and I agree with explanation.



Manager
Status: One Last Shot !!!
Joined: 04 May 2014
Posts: 229
Location: India
Concentration: Marketing, Social Entrepreneurship
GMAT 1: 630 Q44 V32 GMAT 2: 680 Q47 V35

Bunuel wrote: Official Solution:
Statements (1) and (2) by themselves are sufficient. S1 tells us that the last three digits of \(N\) are the same as the first three digits: \(N = abcabc\). Note that \(N = abc*1000 + abc = abc*1001\). As 1001 is divisible by 7, \(N\) is also divisible by 7.
Answer: D Bunuel, thanks for the explanation! I think you missed the explanation for S2. How did we conclude that S2 is sufficient? I just realised that every 6digit number with all same digits is divisible by 7. But, are we supposed to know this or we can prove S2's sufficiency algebraically too?
_________________
One Kudos for an everlasting piece of knowledge is not a bad deal at all...  Twenty years from now you will be more disappointed by the things you didn't do than by the ones you did do. So throw off the bowlines. Sail away from the safe harbor. Catch the trade winds in your sails. Explore. Dream. Discover. Mark Twain



Intern
Joined: 27 Oct 2015
Posts: 19

Re: M1529
[#permalink]
Show Tags
17 Dec 2016, 04:33
Hi Buenel,
Request you to kindly explain algebraically why Statement 2 is sufficient.
Many Thanks.



Retired Moderator
Status: Long way to go!
Joined: 10 Oct 2016
Posts: 1344
Location: Viet Nam

Re: M1529
[#permalink]
Show Tags
17 Dec 2016, 11:51
dsheth7 wrote: Hi Buenel,
Request you to kindly explain algebraically why Statement 2 is sufficient.
Many Thanks. State 2 is explained here m15184061.html#p1420417DarkMight wrote: Dear Bunuel
Could you please tell me what's the reasoning behind Statement 2? Is it the abovediscussed fact with x*111'111? If that is indeed the case, how should one get that 111111 is divisible by 7 within the 2 mins given?:) Would be more than happy to get enlighted...
Thx vm, Dark Might stonecold wrote: mestrec wrote: I think this is a highquality question and the explanation isn't clear enough, please elaborate. If someone could elaborate more... I just cant understand the reasons related at the explanations... I agree with you... And More importantly i am not sure divisibility by 7 is really on the GMAT maybe mikemcgarry can shed some light on whether we really need to do such questions or not .. Regards chirag In my opinion, in actual GMAT, we are not allowed to use calculator, so every calculation is done by ourselves. In case that we face this question, I think we could still complete it under 2 mins. In statement (1), we simply check whether 1001 is divisible by 7 or not. In statement (2), we simply check whether 111,111 is divisible by 7 or not. And the division by 7 is not complex. I believe that anyone could make it in about 10 secs. Here is how I make the calculation Attachment: Untitled.png
>> !!!
You do not have the required permissions to view the files attached to this post.
_________________







Go to page
1 2
Next
[ 30 posts ]



