BREAKING: Target Test Prep releases Brand New 2026 On Demand GMAT prep course

Redeem
TTP OnDemand GMAT Video Course
Featured Course

Target Test Prep GMAT OnDemand

Scott Woodbury-Stewart’s private virtual classroom — 400 hours of master-class video lessons for the GMAT Focus Edition.

  • 715+ score guarantee — highest in the industry (99th percentile)
  • 52 chapters · 1,500+ lessons · 4,000+ practice questions
  • 400 hours of video · 1,500+ instructor-led HD smartboard lessons
  • 300,000+ students accepted to Harvard, Stanford, Wharton, Booth & Sloan & more
  • 24/7 live support + weekly Zoom office hours with GMAT instructors
  • TTP AI Assist — 24/7 AI-powered virtual tutor for instant help
  • 1,200+ flashcards + AI-powered study assistant & daily calendar
  • OnDemand, LiveTeach & GMAT Bootcamp formats available
  • Also: GRE, SAT Math & Executive Assessment courses
  • MBA Admissions Consulting now available
  • 🏆 2025 EdTech Breakthrough Award: Test Prep Solution Provider of the Year
  • 200,000+ students served
  • 5-day free trial — $0 to start, no auto-billing, cancel anytime
★★★★★ 5.0 (559 reviews)
130-pt guarantee
$0 to start then $127/mo
Start Free 5-Day Trial Read 559 Reviews →

ten digit of n

Expert replies
Post new topic Post Reply
Previous Topic Next Topic
Source: — Data Sufficiency |
User avatar
GMAT Instructor
Posts: 15539
Joined: Tue May 25, 2010 12:04 pmFollowed by: 1906 members
Location: New York, NY
Thanked: 13060 times
GMAT Score:790

by GMATGuruNY » Sun Jul 17, 2016 1:55 am
Needgmat wrote:If n is a positive integer, what is the ten digit of n?

1) The hundreds digit of 10n is 6

2) The tens digit of n+1 is 7
Statement 1:
10n = 600, 610, 620, 630...

If we divide both sides by 10, we get the following options for n:
n = 60, 61, 62, 63...
In every case, the tens digit of n is 6.
SUFFICIENT.

Statement 2:
n+1 = 70, 71, 72...

If we subtract 1 from both sides, we get the following options for n:
n = 69, 70, 71...

If n=69, then its tens digit is 6.
If n=70, then its tens digit is 7.
Since the tens digit can be different values, INSUFFICIENT.

The correct answer is A.
Private tutor exclusively for the GMAT and GRE, with over 20 years of experience.
Followed here and elsewhere by over 1900 test-takers.
I have worked with students based in the US, Australia, Taiwan, China, Tajikistan, Kuwait, Saudi Arabia -- a long list of countries.
My students have been admitted to HBS, CBS, Tuck, Yale, Stern, Fuqua -- a long list of top programs.

As a tutor, I don't simply teach you how I would approach problems.
I unlock the best way for YOU to solve problems.

For more information, please email me (Mitch Hunt) at [email protected].
Student Review #1
Student Review #2
Student Review #3
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY

GMAT/MBA Expert

User avatar
GMAT Instructor
Posts: 16207
Joined: Mon Dec 08, 2008 6:26 pmFollowed by: 1268 members
Location: Vancouver, BC
Thanked: 5254 times
GMAT Score:770

by Brent@GMATPrepNow » Sun Jul 17, 2016 5:55 am
Needgmat wrote:If n is a positive integer, what is the ten digit of n?

1) The hundreds digit of 10n is 6

2) The tens digit of n+1 is 7
Target question: What is the tens digit of n?

Statement 1: The hundreds digit of 10n is 6
Notice what happens when we multiply any positive integer by 10:
34 x 10 = 340
60 x 10 = 600
128 x 10 = 1280
54629 x 10 = 546290
The tens digit in the original number becomes the hundreds digit in the new number.

So, if we're told that the hundreds digit of 10n is 6, then we know that the tens digit in n must be 6
Since we can answer the target question with certainty, statement 1 is SUFFICIENT

Statement 2: The tens digit of n+1 is 7
There are several values of n that meet this condition. Here are two:
case a: n=69 in which case the tens digit of n is 6
case b: n=74 in which case the tens digit of n is 7
Since we cannot answer the target question with certainty, statement 2 is NOT SUFFICIENT


Answer = A

Cheers,
Brent
Brent Hanneson - Creator of GMATPrepNow.com
Image
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY

GMAT/MBA Expert

User avatar
Elite Legendary Member
Posts: 10392
Joined: Sun Jun 23, 2013 6:38 pmFollowed by: 511 members
Location: Palo Alto, CA
Thanked: 2867 times
GMAT Score:800

by [email protected] » Sun Jul 17, 2016 9:04 am
Hi Needgmat,

Both Mitch's and Brent's explanations are right-on, so I won't rehash them here. The issue in this question is basically a "decimal shift" issue, which is something you'll see on the GMAT as least once. You will also have to deal with this issue any time the answers having shifting decimals:

For example

210
21
2.1
.21
.021

This is essentially a test of your "accounting" ability - it's really easy to get this question correct and really easy to screw it up. To get the 700+ that everyone's after, you have to be perfect on these questions (in addition to all of the other questions that you need to get correct).

GMAT assassins aren't born, they're made,
Rich
Contact Rich at [email protected]
Image
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
Junior | Next Rank: 30 Posts
Posts: 23
Joined: Mon Feb 06, 2012 5:07 am
Thanked: 1 times

by mjmehta81 » Mon Jul 18, 2016 6:51 am
Hello Mitch Hunt and other experts......

I understood your explanations. Please help me in my below logic where I go wrong..

Statement 1. hundreds digit of 10n is 6...So, let n=61-> so 10n=610.. hundred digit is 6 but ten digit is 1.

let n=62-> .. hundred digit of 10n=620 but ten digit of n is 2.. So INSUFFICIENT.

Statement 2.The tens digit of n+1 is 7. If n is a 2 digit positive integer (to get tens digit atleast) n has to be 69, to get 69+1=70.. so 69...let n=169 so n+1=170.. so still tens digit is 7, but n is 169.. Hence in sufficient..

Both together will say that only with number n=69, 10n=690.. so Statement 1 sufficient and 69+1=70.. So Statement 2 sufficient...

So OA shoudl be C.

Please explain where I go wrong in above explanation.

Regards,

Mrudang
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY

GMAT/MBA Expert

User avatar
GMAT Instructor
Posts: 16207
Joined: Mon Dec 08, 2008 6:26 pmFollowed by: 1268 members
Location: Vancouver, BC
Thanked: 5254 times
GMAT Score:770

by Brent@GMATPrepNow » Mon Jul 18, 2016 7:07 am
mjmehta81 wrote:Hello Mitch Hunt and other experts......

I understood your explanations. Please help me in my below logic where I go wrong..

Statement 1. hundreds digit of 10n is 6...So, let n=61-> so 10n=610.. hundred digit is 6 but ten digit is 1. Here n = 61 and 10n = 610. The question asks for the tens digit of n, not 10n. The tens digit of n is 6

let n=62-> .. hundred digit of 10n=620 but ten digit of n is 2.. So INSUFFICIENT.
Here n = 62 and 10n = 620. The question asks for the tens digit of n, not 10n. The tens digit of n is 6
My comments are above
Brent Hanneson - Creator of GMATPrepNow.com
Image
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
GMAT Instructor
Posts: 2630
Joined: Wed Sep 12, 2012 3:32 pmFollowed by: 119 members
Location: East Bay all the way
Thanked: 625 times
GMAT Score:780

by Matt@VeritasPrep » Fri Jul 22, 2016 1:52 am
mjmehta81 wrote: Statement 1. hundreds digit of 10n is 6...So, let n=61-> so 10n=610.. hundred digit is 6 but ten digit is 1.

let n=62-> .. hundred digit of 10n=620 but ten digit of n is 2.. So INSUFFICIENT.
This is a totally reasonable and common objection, but remember that you don't have to tell us *everything* about n: you only have to give us what the question seeks. Since we're only asked for the tens digit of n, the units digit of n (the tens digit of 10n) is irrelevant.

It's nice to be complete and thorough, but that instinct can get us in real trouble in DS.
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
Post new topic Post Reply
• Page 1 of 1