Find all School-related info fast with the new School-Specific MBA Forum

It is currently 17 Sep 2014, 20:01

Close

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

we will pick new questions that match your level based on your Timer History

Track
Your Progress

every week, we’ll send you an estimated GMAT score based on your performance

Practice
Pays

we will pick new questions that match your level based on your Timer History

Not interested in getting valuable practice questions and articles delivered to your email? No problem, unsubscribe here.

Events & Promotions

Events & Promotions in June
Open Detailed Calendar

If n is a positive integer and the tens digit of n+8 is 6, w

  Question banks Downloads My Bookmarks Reviews Important topics  
Author Message
TAGS:
1 KUDOS received
Director
Director
avatar
Joined: 29 Nov 2012
Posts: 930
Followers: 11

Kudos [?]: 271 [1] , given: 543

If n is a positive integer and the tens digit of n+8 is 6, w [#permalink] New post 18 Aug 2013, 04:31
1
This post received
KUDOS
3
This post was
BOOKMARKED
00:00
A
B
C
D
E

Difficulty:

  95% (hard)

Question Stats:

36% (02:39) correct 64% (01:38) wrong based on 195 sessions
If n is a positive integer and the tens digit of n+8 is 6, what is the tens digit of n?

(1) The units digit of n is a prime number
(2) The tens digit of n-8 is 4


[Reveal] Spoiler:
Any better approach for statement 2?
[Reveal] Spoiler: OA

_________________

Click +1 Kudos if my post helped...

Amazing Free video explanation for all Quant questions from OG 13 and much more http://www.gmatquantum.com/og13th/

GMAT Prep software What if scenarios gmat-prep-software-analysis-and-what-if-scenarios-146146.html

Expert Post
1 KUDOS received
Verbal Forum Moderator
Verbal Forum Moderator
User avatar
Joined: 10 Oct 2012
Posts: 627
Followers: 41

Kudos [?]: 578 [1] , given: 135

Premium Member
Re: If n is a positive integer and the tens digit of n+8 is 6, w [#permalink] New post 18 Aug 2013, 04:39
1
This post received
KUDOS
Expert's post
1
This post was
BOOKMARKED
fozzzy wrote:
If n is a positive integer and the tens digit of n+8 is 6, what is the tens digit of n?

1) The units digit of n is a prime number
2) The tens digit of n-8 is 4


[Reveal] Spoiler:
Any better approach for statement 2?


For F.S 2, we know that n-8 = 4X. Thus, n = 4X+8. Adding 8 on both sides, we get n+8 = 4X+16.
Now, as the tens digit of n+8 is 6, therefore, X can only range from 4 to 9.
Thus, the maximum value of n = 49+8 = 57 and the minimum value of n = 44+8 = 52.

The tens digit of n = 5. Sufficient.
_________________

All that is equal and not-Deep Dive In-equality

Hit and Trial for Integral Solutions

Director
Director
avatar
Joined: 29 Nov 2012
Posts: 930
Followers: 11

Kudos [?]: 271 [0], given: 543

Re: If n is a positive integer and the tens digit of n+8 is 6, w [#permalink] New post 19 Aug 2013, 01:53
Could you elaborate a bit more it isn't very clear. I approached this question differently. Let n = abc

abc
+ 8 in this scenarios b is 6 so c = 0,1,2,3 then we don't get a carryover b=6 but if c=4-9(range) then we get a carryover so b=5

Given statement 1 is sufficient since there will be carryover so c=5

Statement 2

abc
- 8 then in this case b=4 if c=9,8 then there is no carryover in that case c=4 but if c=0-7(range) then b=5

but my question in using this approach c can only be 4,5,6,7 ( I know its irrelevant for this question but I'm asking this for conceptual clarity?)

So can someone explain this part
_________________

Click +1 Kudos if my post helped...

Amazing Free video explanation for all Quant questions from OG 13 and much more http://www.gmatquantum.com/og13th/

GMAT Prep software What if scenarios gmat-prep-software-analysis-and-what-if-scenarios-146146.html

Expert Post
1 KUDOS received
Verbal Forum Moderator
Verbal Forum Moderator
User avatar
Joined: 10 Oct 2012
Posts: 627
Followers: 41

Kudos [?]: 578 [1] , given: 135

Premium Member
Re: If n is a positive integer and the tens digit of n+8 is 6, w [#permalink] New post 19 Aug 2013, 02:21
1
This post received
KUDOS
Expert's post
fozzzy wrote:
Could you elaborate a bit more it isn't very clear. I approached this question differently. Let n = abc

abc
+ 8 in this scenarios b is 6 so c = 0,1,2,3 then we don't get a carryover b=6 but if c=4-9(range) then we get a carryover so b=5

Given statement 1 is sufficient since there will be carryover so c=5

Statement 2

abc
- 8 then in this case b=4 if c=9,8 then there is no carryover in that case c=4 but if c=0-7(range) then b=5

but my question in using this approach c can only be 4,5,6,7 ( I know its irrelevant for this question but I'm asking this for conceptual clarity?)

So can someone explain this part


Could you state exactly which part was not clear?

Anyways, here is another approach : From F.S 2, we know that 40\leq{n-8}\leq{49} \to 48\leq{n}\leq{57}

Also, the question stem states that : 60\leq{n+8}\leq{69} \to 52\leq{n}\leq{61}

The common intersection of both the in-equalities is \to 52\leq{n}\leq{57}. So , yes, "c" as in your example can range only from 2 to 7.

Hope this is clear.

Note: When I say 52\leq{n}\leq{57}, it doesn't mean that n is a 2 digit number. It is just a scalable inequality for its last 2 digits.
_________________

All that is equal and not-Deep Dive In-equality

Hit and Trial for Integral Solutions

Expert Post
Math Expert
User avatar
Joined: 02 Sep 2009
Posts: 29671
Followers: 3496

Kudos [?]: 26292 [0], given: 2708

Re: If n is a positive integer and the tens digit of n+8 is 6, w [#permalink] New post 19 Aug 2013, 02:30
Expert's post
fozzzy wrote:
If n is a positive integer and the tens digit of n+8 is 6, what is the tens digit of n?

(1) The units digit of n is a prime number
(2) The tens digit of n-8 is 4


[Reveal] Spoiler:
Any better approach for statement 2?


Similar questions to practice:
if-z-is-a-three-digit-positive-integer-what-is-the-value-of-69999.html
if-the-units-digit-of-the-three-digit-positive-integer-k-is-85443.html
both-a-b-and-c-are-3-digits-integers-where-a-b-c-is-the-126570.html
if-k-is-a-3-digit-positive-number-what-is-the-hundred-digit-104529.html
if-k-is-a-positive-integer-and-the-tens-digit-of-k-5-is-100041.html

Hope it helps.
_________________

NEW TO MATH FORUM? PLEASE READ THIS: ALL YOU NEED FOR QUANT!!!

PLEASE READ AND FOLLOW: 11 Rules for Posting!!!

RESOURCES: [GMAT MATH BOOK]; 1. Triangles; 2. Polygons; 3. Coordinate Geometry; 4. Factorials; 5. Circles; 6. Number Theory; 7. Remainders; 8. Overlapping Sets; 9. PDF of Math Book; 10. Remainders; 11. GMAT Prep Software Analysis NEW!!!; 12. SEVEN SAMURAI OF 2012 (BEST DISCUSSIONS) NEW!!!; 12. Tricky questions from previous years. NEW!!!;

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?
25 extra-hard Quant Tests

Get the best GMAT Prep Resources with GMAT Club Premium Membership

Expert Post
Moderator
Moderator
User avatar
Affiliations: GMAT Club
Joined: 21 Feb 2012
Posts: 1181
Location: India
City: Pune
GPA: 3.4
WE: Business Development (Manufacturing)
Followers: 146

Kudos [?]: 914 [0], given: 873

GMAT ToolKit User Premium Member CAT Tests
Re: If n is a positive integer and the tens digit of n+8 is 6, w [#permalink] New post 19 Aug 2013, 12:51
Expert's post
Ques :- If n is a positive integer and the tens digit of n+8 is 6, what is the tens digit of n?

Tens digit of n+8 is 6, So lets assume that n+8 is 6b, where b is units digit.
We are asked the tens digit of n. that means ques is indirectly asking that if we subtract 8 from 6b (i.e. from n+8) would the tens digit reduce from 6 to 5?

Further examination would tell us that if b takes any value from 0 to 7 tens digit will become 5 (i.e. will change) and it b takes value of 8 or 9 tens digit will remain same because when smaller units digit subtracted from larger units digit, the subtraction would not affect the tens digit.

So the question is basically asking us What is the units digit of n?


(1) The units digit of n is a prime number :- Units digit is one from 1,2,5,7. All these values are below 8. So we can say tens digit of n is 5. Sufficient

(2) The tens digit of n-8 is 4 :- This is tricky. (n+8) and (n-8) have difference of 16. n+8 has tens digit as 6 and n-8 has tens digit as 4. So these numbers must be of the form 6b (59<6b<70) and 4a (39<4a<50)
The only pairs of the numbers that obeys above conditions and differed by 16 are as follows
44 and 60
45 and 61
46 and 62
47 and 63
48 and 64
49 and 65
In all the cases we can see the units digit of all 6b (i.e. of n+8) lies between 0 and 5. That means it is below 8. So tens digit of n is 5. Sufficient

Answer D
_________________

Be the coolest guy in the MBA Forum - Be a threadmaster!

Have a blog? Feature it on GMAT Club!

All MBA Resources All 'Sticky' Topics at one place

Please share your profiles for this application season: 2015 Profiles w/ Admit/Dings Results!

Get the best GMAT Prep Resources with GMAT Club Premium Membership

Next Generation GMATClub CATS with Brilliant Analytics.


Director
Director
avatar
Joined: 29 Nov 2012
Posts: 930
Followers: 11

Kudos [?]: 271 [0], given: 543

Re: If n is a positive integer and the tens digit of n+8 is 6, w [#permalink] New post 19 Aug 2013, 23:43
@Narenn shouldn't the tens digit be 5? The total sum is 6 ( when its carried over)
_________________

Click +1 Kudos if my post helped...

Amazing Free video explanation for all Quant questions from OG 13 and much more http://www.gmatquantum.com/og13th/

GMAT Prep software What if scenarios gmat-prep-software-analysis-and-what-if-scenarios-146146.html

Expert Post
Moderator
Moderator
User avatar
Affiliations: GMAT Club
Joined: 21 Feb 2012
Posts: 1181
Location: India
City: Pune
GPA: 3.4
WE: Business Development (Manufacturing)
Followers: 146

Kudos [?]: 914 [0], given: 873

GMAT ToolKit User Premium Member CAT Tests
Re: If n is a positive integer and the tens digit of n+8 is 6, w [#permalink] New post 20 Aug 2013, 01:26
Expert's post
Yeah, You were correct. Ten's digit should be 5. There was a typing mistake, which I just corrected.

Thanks
_________________

Be the coolest guy in the MBA Forum - Be a threadmaster!

Have a blog? Feature it on GMAT Club!

All MBA Resources All 'Sticky' Topics at one place

Please share your profiles for this application season: 2015 Profiles w/ Admit/Dings Results!

Get the best GMAT Prep Resources with GMAT Club Premium Membership

Next Generation GMATClub CATS with Brilliant Analytics.


SVP
SVP
User avatar
Joined: 06 Sep 2013
Posts: 1664
Location: United States
Concentration: Finance
GMAT 1: 710 Q48 V39
WE: Corporate Finance (Investment Banking)
Followers: 12

Kudos [?]: 164 [0], given: 268

GMAT ToolKit User
Re: If n is a positive integer and the tens digit of n+8 is 6, w [#permalink] New post 12 Feb 2014, 09:11
Narenn wrote:
Yeah, You were correct. Ten's digit should be 5. There was a typing mistake, which I just corrected.

Thanks


There's no need for all this. From statement 2 we have that n - 8 tens digit 4. We had that n+8 tens digit 6. Therefore, only tens digit that is possible is 5, since both are 16 apart.

Hope this clarifies
Cheers
J
Intern
Intern
avatar
Joined: 21 May 2013
Posts: 3
Schools: Tuck '17, Duke '17
Followers: 0

Kudos [?]: 0 [0], given: 22

Re: If n is a positive integer and the tens digit of n+8 is 6, w [#permalink] New post 12 Aug 2014, 11:52
Guys I think the answer should be B. For A what about 28+8 or 38+8 we can never find out what the tens digit is.what do you say?
Intern
Intern
avatar
Joined: 13 May 2014
Posts: 2
Followers: 0

Kudos [?]: 0 [0], given: 10

CAT Tests
Re: If n is a positive integer and the tens digit of n+8 is 6, w [#permalink] New post 12 Aug 2014, 23:05
Let ....yx be he number n where y is ten's digit and x is unit'd digit.

Given information : ten's digit of (n+8) =6
It means two possibilites :-
<1> y=6 ,x=0,1
<2>y=5,x>=2
Now let's go to options:-

<A> Unit digit is a prime number
It means x=2 or 3 or 5 or 7
This imples y=5 Hence ,ten's digit of n can be uniquely determined as 5
<B> ten's digit of (n-8)=4
It means two possibilities :-
<1> y=4,x=8,9
<2> y=5,x=1,2,3,4,5,6,7
This means y=5 as from given information y=5 or 6.

Hence , option D ,Each statement is suffiecient alone
Expert Post
1 KUDOS received
Math Expert
User avatar
Joined: 02 Sep 2009
Posts: 29671
Followers: 3496

Kudos [?]: 26292 [1] , given: 2708

Re: If n is a positive integer and the tens digit of n+8 is 6, w [#permalink] New post 13 Aug 2014, 01:54
1
This post received
KUDOS
Expert's post
KS15 wrote:
Guys I think the answer should be B. For A what about 28+8 or 38+8 we can never find out what the tens digit is.what do you say?


Notice that we are told that the tens digit of n+8 is 6. In your examples, the tens digit of 28+8=36 is 3, not 6 and the tens digit of 38+8=46 is 4, not 6. Also, the first statement says that the units digit of n is a prime number, and 8 (the units digit of 28 and 38), is NOT a prime.

Consider number 1234.567

1 - THOUSANDS
2 - HUNDREDS
3 - TENS
4 - UNITS
. - decimal point
5 - TENTHS
6 - HUNDREDTHS
7 - THOUSANDTHS

Hope this helps.
_________________

NEW TO MATH FORUM? PLEASE READ THIS: ALL YOU NEED FOR QUANT!!!

PLEASE READ AND FOLLOW: 11 Rules for Posting!!!

RESOURCES: [GMAT MATH BOOK]; 1. Triangles; 2. Polygons; 3. Coordinate Geometry; 4. Factorials; 5. Circles; 6. Number Theory; 7. Remainders; 8. Overlapping Sets; 9. PDF of Math Book; 10. Remainders; 11. GMAT Prep Software Analysis NEW!!!; 12. SEVEN SAMURAI OF 2012 (BEST DISCUSSIONS) NEW!!!; 12. Tricky questions from previous years. NEW!!!;

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?
25 extra-hard Quant Tests

Get the best GMAT Prep Resources with GMAT Club Premium Membership

Re: If n is a positive integer and the tens digit of n+8 is 6, w   [#permalink] 13 Aug 2014, 01:54
    Similar topics Author Replies Last post
Similar
Topics:
1 If n is a positive integer, what is the tens digit of n ? sehosayho 1 26 May 2014, 20:12
10 Experts publish their posts in the topic If n is a positive integer, what is the tens digit of n ? Walkabout 4 26 Dec 2012, 04:51
3 If n is a positive integer, what is the tens digit of n ? siddhans 8 10 Jun 2011, 23:47
Experts publish their posts in the topic If n is a positive integer, what is the tens digit of n ? Baten80 4 25 Feb 2011, 04:12
Experts publish their posts in the topic If n is a positive integer, what is the tens digit of n ? mbassmbass04 4 18 Dec 2004, 16:39
Display posts from previous: Sort by

If n is a positive integer and the tens digit of n+8 is 6, w

  Question banks Downloads My Bookmarks Reviews Important topics  


GMAT Club MBA Forum Home| About| Privacy Policy| Terms and Conditions| GMAT Club Rules| Contact| Sitemap

Powered by phpBB © phpBB Group and phpBB SEO

Kindly note that the GMAT® test is a registered trademark of the Graduate Management Admission Council®, and this site has neither been reviewed nor endorsed by GMAC®.