GMAT Question of the Day - Daily to your Mailbox; hard ones only

It is currently 18 Nov 2018, 04:38

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.

Close

Request Expert Reply

Confirm Cancel
Events & Promotions in November
PrevNext
SuMoTuWeThFrSa
28293031123
45678910
11121314151617
18192021222324
2526272829301
Open Detailed Calendar
  • How to QUICKLY Solve GMAT Questions - GMAT Club Chat

     November 20, 2018

     November 20, 2018

     09:00 AM PST

     10:00 AM PST

    The reward for signing up with the registration form and attending the chat is: 6 free examPAL quizzes to practice your new skills after the chat.
  • The winning strategy for 700+ on the GMAT

     November 20, 2018

     November 20, 2018

     06:00 PM EST

     07:00 PM EST

    What people who reach the high 700's do differently? We're going to share insights, tips and strategies from data we collected on over 50,000 students who used examPAL.

D represents a single digit number from 1 to 9. What is the value of D

  new topic post reply Question banks Downloads My Bookmarks Reviews Important topics  
Author Message
TAGS:

Hide Tags

Math Expert
User avatar
V
Joined: 02 Sep 2009
Posts: 50626
D represents a single digit number from 1 to 9. What is the value of D  [#permalink]

Show Tags

New post 28 Jul 2017, 00:23
00:00
A
B
C
D
E

Difficulty:

  45% (medium)

Question Stats:

71% (01:52) correct 29% (02:12) wrong based on 238 sessions

HideShow timer Statistics

D represents a single digit number from 1 to 9. What is the value of D?

(1) D.D + DD = D.D × DD
(2) D is not a prime number.

The dot (.) represents a decimal point.

_________________

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?
Extra-hard Quant Tests with Brilliant Analytics

Director
Director
User avatar
P
Joined: 18 Aug 2016
Posts: 625
Concentration: Strategy, Technology
GMAT 1: 630 Q47 V29
GMAT 2: 740 Q51 V38
GMAT ToolKit User Premium Member Reviews Badge
Re: D represents a single digit number from 1 to 9. What is the value of D  [#permalink]

Show Tags

New post 28 Jul 2017, 00:48
1
Bunuel wrote:
D represents a single digit number from 1 to 9. What is the value of D?

(1) D.D + DD = D.D × DD
(2) D is not a prime number.

The dot (.) represents a decimal point.


(1) D.D + DD = D.D × DD
1.1 + 11 = 1.1 * 11 Yes
2.2 + 22 = 2.2 * 22 No

9.9 + 99 = 9.9 * 99 No (Only D=1 can hold)

Sufficient

(2) D can represent 2, 3, 5, 7...Not Sufficient

A
_________________

We must try to achieve the best within us


Thanks
Luckisnoexcuse

Intern
Intern
avatar
B
Joined: 21 Jun 2017
Posts: 10
GMAT 1: 750 Q50 V41
Re: D represents a single digit number from 1 to 9. What is the value of D  [#permalink]

Show Tags

New post 30 Jul 2017, 10:09
(1)Sufficient
D +D/10 + 11D = (D+D/10)*11D
-> 121D = 121D^2
-> D(D-1) = 0
D is from 1-9 so D =1
(2) Not
D can be 1,4,6,8,9
Intern
Intern
avatar
B
Joined: 18 Aug 2017
Posts: 30
GMAT 1: 670 Q49 V33
Re: D represents a single digit number from 1 to 9. What is the value of D  [#permalink]

Show Tags

New post 24 Aug 2017, 00:15
2
My approach:

1- Let 2 digit number DD is a, then D.D = a/10

a/10 + a = a/10 x a
11a/10 = a^2 /10
11 = a (a is positive so we can get rid of a/10 on both side)

so D = 1 => SUFF

2- D not prime, so D can be 4, 6, 8 => INSUFF

A is the answer.
Senior Manager
Senior Manager
avatar
S
Joined: 15 Jan 2017
Posts: 359
Re: D represents a single digit number from 1 to 9. What is the value of D  [#permalink]

Show Tags

New post 14 Sep 2017, 13:40
Tried plugging in, which worked:
1) 22*2.2 = 22+2.2 not possible
11*1.1 = 11+ 1.1 --> possible
Suff
2) D not prime -- multiple values possible then. Not suff

Ans A
EMPOWERgmat Instructor
User avatar
V
Status: GMAT Assassin/Co-Founder
Affiliations: EMPOWERgmat
Joined: 19 Dec 2014
Posts: 12877
Location: United States (CA)
GMAT 1: 800 Q51 V49
GRE 1: Q170 V170
Re: D represents a single digit number from 1 to 9. What is the value of D  [#permalink]

Show Tags

New post 17 Dec 2017, 14:17
Hi All,

This question can be solved with a little math and a bit of 'brute force.'

We're told that D is a positive DIGIT (meaning 1-9, inclusive). We're asked for the value of D.

1) D.D + DD = (D.D)(DD)

While this might look complex, if you substitute in a value for D, you'll find that math to be rather straight-forward....

IF.... D = 1, we have...
1.1 + 11 = (1.1)(11)

Does that equation 'balance out?'
1.1 + 11 = 12.1
(1.1)(11) = 12.1
So YES, D could equal 1.

What about D = 2? Does....
2.2 + 22 = (2.2)(22)

You should be able to answer that question WITHOUT actually doing the math. On the left side, you're ADDING 10% of 22 to 22 and on the right side you're MULTIPLYING those values. The right side will clearly be a lot bigger than the left side. This means that D CANNOT equal 2.

Now how about D=3? D=4? Etc. You should see that you run into the same issue that you did when we worked through D=2: the right side is much bigger than the left side, so there's really no need to check all of those values. This means that D=1 is the ONLY possible solution.
Fact 1 is SUFFICIENT.

2) D is not a prime number

This tells us that D cannot be 2, 3, 5 or 7.... but that still leaves us with 5 other possibilities (1, 4, 6, 8 and 9)
Fact 2 is INSUFFICIENT.

Final Answer:

GMAT assassins aren't born, they're made,
Rich
_________________

760+: Learn What GMAT Assassins Do to Score at the Highest Levels
Contact Rich at: Rich.C@empowergmat.com

Rich Cohen

Co-Founder & GMAT Assassin

Special Offer: Save $75 + GMAT Club Tests Free
  Official GMAT Exam Packs + 70 Pt. Improvement Guarantee
www.empowergmat.com/

*****Select EMPOWERgmat Courses now include ALL 6 Official GMAC CATs!*****

Intern
Intern
avatar
B
Joined: 10 Feb 2018
Posts: 5
Re: D represents a single digit number from 1 to 9. What is the value of D  [#permalink]

Show Tags

New post 08 Apr 2018, 05:11
Bunuel wrote:
D represents a single digit number from 1 to 9. What is the value of D?

(1) D.D + DD = D.D × DD
(2) D is not a prime number.

The dot (.) represents a decimal point.


by statement 1,

D.D + DD = (D.D) (DD)
\(\frac{DD}{10}+ DD = \frac{DD}{10} (DD)\)
DD + 10DD = (DD) (DD)
11DD = (DD) (DD)
DD = 11

therefore, statement 1 is sufficient.

Statement 2 gives no proper information.

Therefore answer is A.


Please correct me if my solution is wrong.
Thanks
Intern
Intern
avatar
B
Joined: 24 Jan 2018
Posts: 1
Premium Member
Re: D represents a single digit number from 1 to 9. What is the value of D  [#permalink]

Show Tags

New post 08 Apr 2018, 08:44
(1) DD+D.D=DD*D.D
=DD(1+1/10)=(DD^2)/10
=11/10=DD/10
DD=11
SUFFICIENT

(2) D can represent 2, 3, 5, 7...NOT SUFFICIENT
GMAT Club Bot
Re: D represents a single digit number from 1 to 9. What is the value of D &nbs [#permalink] 08 Apr 2018, 08:44
Display posts from previous: Sort by

D represents a single digit number from 1 to 9. What is the value of D

  new topic post reply Question banks Downloads My Bookmarks Reviews Important topics  


Copyright

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

Powered by phpBB © phpBB Group | Emoji artwork provided by EmojiOne

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®.