It is currently 21 Jan 2018, 12:09

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

Events & Promotions in June
Open Detailed Calendar

If A & B are positive integers, is a^2 + b^2 divisible

  post reply Question banks Downloads My Bookmarks Reviews Important topics  
Author Message
CEO
CEO
User avatar
Joined: 21 Jan 2007
Posts: 2734

Kudos [?]: 1114 [0], given: 4

Location: New York City
If A & B are positive integers, is a^2 + b^2 divisible [#permalink]

Show Tags

New post 15 Nov 2007, 01:53
1
This post was
BOOKMARKED
00:00
A
B
C
D
E

Difficulty:

(N/A)

Question Stats:

0% (00:00) correct 0% (00:00) wrong based on 17 sessions

HideShow timer Statistics

This topic is locked. If you want to discuss this question please re-post it in the respective forum.

If A & B are positive integers, is a^2 + b^2 divisible by 5?

1. 2AB is divisible by 5
2. A-B is divisible by 5


Can someone walk me thru the solution

Kudos [?]: 1114 [0], given: 4

Intern
Intern
avatar
Joined: 14 Nov 2007
Posts: 10

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

Re: DS 19.11 Divisibility [#permalink]

Show Tags

New post 15 Nov 2007, 02:32
bmwhype2 wrote:
If A & B are positive integers, is a^2 + b^2 divisible by 5?

1. 2AB is divisible by 5
2. A-B is divisible by 5


Can someone walk me thru the solution


It seems like E is here. I just took 2 examples :

1) 7 and 6 : 7^2+6^2 = 85 which is divisible by 5
On the other hand 7-6 is not divisible by 5 and 7*6*2 is not divisible by 5

2) the other story is 10 and 5 10^2 + 5^2 = 125 which is divisible by 5.
10-5 anf 10*5*2 are both divisible by 5.

Therefore - E

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

Director
Director
avatar
Joined: 09 Aug 2006
Posts: 754

Kudos [?]: 273 [0], given: 0

Re: DS 19.11 Divisibility [#permalink]

Show Tags

New post 15 Nov 2007, 06:13
bmwhype2 wrote:
If A & B are positive integers, is a^2 + b^2 divisible by 5?

1. 2AB is divisible by 5
2. A-B is divisible by 5


Can someone walk me thru the solution


C.

Stat 1: Tells us that at least one of A and B is divisible by 5. If A = 10 and B = 5 then answer to stem is yes. If A = 10 and B = 2 then answer to stem is no. Insuff.

Stat 2: Tells us that A-B is a multiple of 5 but says nothing about A or B. If A = 10 & B = 5 answer to stem is yes. If A = 12 & B = 7 answer to stem is no. Insuff.

Together: Since A (or B) has to be a multiple of 5 according to stat 1, B (or A) has to be a multiple of 5 as well for stat 2 to be true. (Multiple of 5)^2 + (Multiple of 5)^2 has to be divisible by 5. Suff.

Kudos [?]: 273 [0], given: 0

Manager
Manager
avatar
B
Joined: 21 Jun 2007
Posts: 146

Kudos [?]: 12 [0], given: 0

Schools: UCLA Anderson School of Mgmt (FEMBA Class of 2013)
WE 1: 7.5 years in Engg. Consulting
 [#permalink]

Show Tags

New post 15 Nov 2007, 06:56
First, I will reword the qn in to

a^2 + b^2 = (a-b)^2 +2ab

Statement 1: 2ab is divisible by 5, does not help much unless the first part is divisible by 5, so not sufficient.

Statement 2: Says a-b is divisible by 5, so (a-b)^ 2 will be divisible by 5, but as Statement 1 unless 2ab is also divisible by 5, the whole expression will not be, so not sufficient.

Both statement combined, we can say the expression is divisible by 5.

So is the answer D?

Kudos [?]: 12 [0], given: 0

Director
Director
User avatar
Joined: 13 Dec 2006
Posts: 506

Kudos [?]: 255 [0], given: 0

Location: Indonesia
 [#permalink]

Show Tags

New post 15 Nov 2007, 07:03
Dear Soomodh,

you have calculated correctly but in that case answer will be C and not D.

Amar

Kudos [?]: 255 [0], given: 0

Non-Human User
User avatar
Joined: 09 Sep 2013
Posts: 14203

Kudos [?]: 291 [0], given: 0

Premium Member
Re: If A & B are positive integers, is a^2 + b^2 divisible [#permalink]

Show Tags

New post 29 Sep 2017, 14:27
Hello from the GMAT Club BumpBot!

Thanks to another GMAT Club member, I have just discovered this valuable topic, yet it had no discussion for over a year. I am now bumping it up - doing my job. I think you may find it valuable (esp those replies with Kudos).

Want to see all other topics I dig out? Follow me (click follow button on profile). You will receive a summary of all topics I bump in your profile area as well as via email.
_________________

GMAT Books | GMAT Club Tests | Best Prices on GMAT Courses | GMAT Mobile App | Math Resources | Verbal Resources

Kudos [?]: 291 [0], given: 0

Re: If A & B are positive integers, is a^2 + b^2 divisible   [#permalink] 29 Sep 2017, 14:27
Display posts from previous: Sort by

If A & B are positive integers, is a^2 + b^2 divisible

  post reply Question banks Downloads My Bookmarks Reviews Important topics  


GMAT Club MBA Forum Home| About| Terms and Conditions| 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®.