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

It is currently 21 Oct 2018, 20:35

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

Arnold and Danny are two twin brothers that are celebrating their birt

  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: 50009
Arnold and Danny are two twin brothers that are celebrating their birt  [#permalink]

Show Tags

New post 13 Jul 2016, 01:52
00:00
A
B
C
D
E

Difficulty:

  45% (medium)

Question Stats:

70% (01:21) correct 30% (01:43) wrong based on 46 sessions

HideShow timer Statistics

Arnold and Danny are two twin brothers that are celebrating their birthday. The product of their ages today is smaller by 9 from the product of their ages a year from today. What is their age today?

A. 2.
B. 4.
C. 5.
D. 7.
E. 9.

_________________

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

Intern
Intern
avatar
B
Joined: 03 Aug 2015
Posts: 35
GMAT ToolKit User
Re: Arnold and Danny are two twin brothers that are celebrating their birt  [#permalink]

Show Tags

New post 13 Jul 2016, 02:24
Let the age be x and after one year the age be x+1.. now as per the given statement :

(X+1)^2 -x^2 = 9

solving we get x=4 hence B
Retired Moderator
avatar
G
Joined: 26 Nov 2012
Posts: 593
Premium Member
Arnold and Danny are two twin brothers that are celebrating their birt  [#permalink]

Show Tags

New post 13 Jul 2016, 02:46
1
Bunuel wrote:
Arnold and Danny are two twin brothers that are celebrating their birthday. The product of their ages today is smaller by 9 from the product of their ages a year from today. What is their age today?

A. 2.
B. 4.
C. 5.
D. 7.
E. 9.




Given Arnold and Danny age be X ( as they are twin brothers will have same age ).

Given the product of their ages is smaller by 9 from the product of their ages a year from today.

The product of their ages as of today be \(X^2\).

Since we are dealing with past year, then their age is also increased by 1 year.

\((X + 1)^2\).

Now difference \((X + 1)^2\) - \(X^2\) = 9.

=> 2X + 1 = 9.

=> 2X = 8. => X = 4.

IMO B is correct option.

OA please...will correct if I missed anything.
Current Student
User avatar
Joined: 18 Oct 2014
Posts: 856
Location: United States
GMAT 1: 660 Q49 V31
GPA: 3.98
GMAT ToolKit User
Re: Arnold and Danny are two twin brothers that are celebrating their birt  [#permalink]

Show Tags

New post 13 Jul 2016, 05:03
Bunuel wrote:
Arnold and Danny are two twin brothers that are celebrating their birthday. The product of their ages today is smaller by 9 from the product of their ages a year from today. What is their age today?

A. 2.
B. 4.
C. 5.
D. 7.
E. 9.


ad = (a+1) (d+1) -9

0= a+d-8

a+d = 8

a=d (as they are twin brothers)

a=d=4

B is the answer
_________________

I welcome critical analysis of my post!! That will help me reach 700+

Target Test Prep Representative
User avatar
G
Status: Head GMAT Instructor
Affiliations: Target Test Prep
Joined: 04 Mar 2011
Posts: 2830
Re: Arnold and Danny are two twin brothers that are celebrating their birt  [#permalink]

Show Tags

New post 29 Jan 2018, 10:42
Bunuel wrote:
Arnold and Danny are two twin brothers that are celebrating their birthday. The product of their ages today is smaller by 9 from the product of their ages a year from today. What is their age today?

A. 2.
B. 4.
C. 5.
D. 7.
E. 9.


If we let Arnold's and Danny’s age today = n, then their ages one year from today will be (n + 1). Thus, we have:

n^2 + 9 = (n + 1)(n + 1)

n^2 + 9 = n^2 + 2n + 1

8 = 2n

4 = n

Answer: B
_________________

Jeffery Miller
Head of GMAT Instruction

GMAT Quant Self-Study Course
500+ lessons 3000+ practice problems 800+ HD solutions

GMAT Club Bot
Re: Arnold and Danny are two twin brothers that are celebrating their birt &nbs [#permalink] 29 Jan 2018, 10:42
Display posts from previous: Sort by

Arnold and Danny are two twin brothers that are celebrating their birt

  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®.