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

It is currently 29 Jul 2014, 02:56

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 the units digit of a^2 + b^2 is 7, which of the following

  Question banks Downloads My Bookmarks Reviews Important topics  
Author Message
TAGS:
Manager
Manager
avatar
Joined: 14 May 2005
Posts: 85
Location: San Francisco
Followers: 1

Kudos [?]: 2 [0], given: 0

GMAT Tests User
If the units digit of a^2 + b^2 is 7, which of the following [#permalink] New post 06 Nov 2006, 00:47
00:00
A
B
C
D
E

Difficulty:

(N/A)

Question Stats:

0% (00:00) correct 0% (00:00) wrong based on 0 sessions
If the units digit of a^2 + b^2 is 7, which of the following could be the units digit of a + b?

3
4
6
8
9
VP
VP
User avatar
Joined: 25 Jun 2006
Posts: 1176
Followers: 2

Kudos [?]: 31 [0], given: 0

GMAT Tests User
 [#permalink] New post 06 Nov 2006, 01:16
A for me.


the possible combinations are:
a has 1 or 9 as unit digit.
b has 6 or 4 as unit digit.

so only A is possible when a has 9 and b has 4 as unit digit.
SVP
SVP
User avatar
Joined: 01 May 2006
Posts: 1816
Followers: 8

Kudos [?]: 86 [0], given: 0

GMAT Tests User
 [#permalink] New post 06 Nov 2006, 01:30
(A) for me.

unitDig(x) -> unitDig(x^2)
0 -> 0
1 -> 1
2 -> 4
3 -> 9
4 -> 6
5 -> 5
6 -> 6
7 -> 9
8 -> 4
9 -> 1

The only combination to obtain 7 is 1 + 6. Thus,
we can search and sum the possible unitDig(x):
o 1+4 = 5
o 1+6 = 7
o 4+9 = 13 : Bingo, the unit is 3
o 6+9 = 15
VP
VP
avatar
Joined: 15 Jul 2004
Posts: 1474
Schools: Wharton (R2 - submitted); HBS (R2 - submitted); IIMA (admitted for 1 year PGPX)
Followers: 15

Kudos [?]: 92 [0], given: 13

GMAT Tests User
 [#permalink] New post 07 Nov 2006, 03:17
Getting A as well.

of the possible SQUARE digits we have 1, 4, 5, 6, and 9 out of which only 1 and 6 yield 7.

1 and 6 can in turn be obtained from

1, 9

4 and 6

so possible options are 3 and 5. A is right.
Manager
Manager
avatar
Joined: 14 May 2005
Posts: 85
Location: San Francisco
Followers: 1

Kudos [?]: 2 [0], given: 0

GMAT Tests User
 [#permalink] New post 12 Nov 2006, 14:31
The OA is A (3).

Thanks the for the responses.
  [#permalink] 12 Nov 2006, 14:31
    Similar topics Author Replies Last post
Similar
Topics:
8 Experts publish their posts in the topic If a^2b^2c^3 = 4500. Is b+c = 7 ? GMATBaumgartner 9 17 Oct 2012, 00:52
9 Experts publish their posts in the topic If a^2b^2c^3 = 4500. Is b+c = 7? MichelleSavina 12 22 Jan 2011, 00:11
If a is a positive integer, and if units digit of a^2 is 9 shehreenquayyum 9 02 Jul 2006, 11:47
If ab does not = 0 and a^2*b^2-ab= 6, which of the following positive soul 4 25 Jun 2006, 01:12
If a + b = a^2 - b^2 and ab > 0, which of the following sandalphon 4 20 Dec 2005, 08:09
Display posts from previous: Sort by

If the units digit of a^2 + b^2 is 7, which of the following

  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®.