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

It is currently 31 Oct 2014, 10:05

Today

Waiting for Decisions? Join us in the chat | All GMAT Club Tests are Free and Open


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

Three questions from the gmat prep

  Question banks Downloads My Bookmarks Reviews Important topics  
Author Message
TAGS:
Intern
Intern
avatar
Joined: 26 May 2009
Posts: 6
Followers: 0

Kudos [?]: 1 [0], given: 3

Three questions from the gmat prep [#permalink] New post 28 May 2009, 21:42
1
This post was
BOOKMARKED
00:00
A
B
C
D
E

Difficulty:

(N/A)

Question Stats:

0% (00:00) correct 100% (01:54) wrong based on 3 sessions
EDIT: 1 more question added, see my last post at the end of this page

Hi guys,

I need help with the following three questions as i really have no clue on how to derive the answers. I greatly appreciate your help.






1. What is the greatest prime factor of 4^17 - 2^28?

A. 2
B. 3
C. 5
D. 7
E. 11


2. attached
Attachment:
1.gif
1.gif [ 11.39 KiB | Viewed 1259 times ]

3. attached
Attachment:
Untitled-2.gif
Untitled-2.gif [ 1.18 KiB | Viewed 1259 times ]

Last edited by steliossb on 29 May 2009, 09:01, edited 2 times in total.
1 KUDOS received
Director
Director
avatar
Joined: 23 May 2008
Posts: 840
Followers: 3

Kudos [?]: 32 [1] , given: 0

Re: Three questions from the gmat prep [#permalink] New post 28 May 2009, 23:00
1
This post received
KUDOS
the first question has been recently discussed here. You can do a search for that one.

I'll take a crack at the other two


problem 2.

let q and m=quotients

given:

n=3q+2, t=5m+3

what is the remainder when nt/15?

nt/15= (3q+2)(5m+3)/15=

(15qm+9q+10m+6)/15


1) (n-2)/5 is an integer

n=3q+2 so 3q/5 is an integer

since 3 and 5 are prime q must be a multiple of 5

plugging into our equation 15qm+9q+10m+6)/15, we see that the first and second terms are multiples of 15, but we dont no about the third term

so insufficient


2) t/3 is an integer so t is a multiple of 3

t=5m+3 so m must be a multiple of 3 as well

plugging into our equation 15qm+9q+10m+6)/15 we find that the first and third terms are multiples of 15 but we dont know about the second term

so insufficient

togther we know all terms are multiples of 15 and the remainder is 6
sufficient

C


problem 3.

if x is -tive then whats the sqrt of -xlxl ?

if x is -tive then -x is x and lxl is also x so the sqrt of x^2 is x

so D
1 KUDOS received
Intern
Intern
avatar
Joined: 12 May 2009
Posts: 48
Location: Mumbai
Followers: 1

Kudos [?]: 3 [1] , given: 1

Re: Three questions from the gmat prep [#permalink] New post 29 May 2009, 01:51
1
This post received
KUDOS
(1) Prime factor is 2.

4^17 - 2^28 = 2^34 - 2^28 = 2^6 = 64
So 2 is the only prime factor for 64

(2) Answer is C, we can derive the conclusion only with both the statements

(3) Since X < 0, it has to be a -ve number.
If X = -2
So, substitute -2 in the equation
Sqrt (-(-2)|-2|) = Sqrt (2*2) = 2

We took X = -2 and got an answer as 2, so the value will be -X
So I would go for -X, Option A


Thanks,
2 KUDOS received
Manager
Manager
avatar
Joined: 12 Apr 2006
Posts: 220
Location: India
Followers: 1

Kudos [?]: 21 [2] , given: 17

Re: Three questions from the gmat prep [#permalink] New post 29 May 2009, 05:37
2
This post received
KUDOS
vesam wrote:
(1) Prime factor is 2.

4^17 - 2^28 = 2^34 - 2^28 = 2^6 = 64
So 2 is the only prime factor for 64



You can't add or subtract exponential power in addition and subtraction of bases.

Powers would be added or subtracted in case of multiplication and division only.

4^17 - 2^28 = 4^17 - 4^14 = 4^14 ( 4^3 - 1) = 4^14*63 = 4^14*7*9.

Greatest prime factor = 7

Last edited by humans on 29 May 2009, 09:58, edited 1 time in total.
Intern
Intern
avatar
Joined: 12 May 2009
Posts: 48
Location: Mumbai
Followers: 1

Kudos [?]: 3 [0], given: 1

Re: Three questions from the gmat prep [#permalink] New post 29 May 2009, 06:59
I misread the question.
Thanks for the correct answer.
Intern
Intern
avatar
Joined: 26 May 2009
Posts: 6
Followers: 0

Kudos [?]: 1 [0], given: 3

Re: Three questions from the gmat prep [#permalink] New post 29 May 2009, 07:29
thanks a lot for the help guys, it was extremely useful.

last question i have for these forums:

Attachment:
4.gif
4.gif [ 5.41 KiB | Viewed 1183 times ]
Manager
Manager
avatar
Joined: 12 Apr 2006
Posts: 220
Location: India
Followers: 1

Kudos [?]: 21 [0], given: 17

Re: Three questions from the gmat prep [#permalink] New post 29 May 2009, 10:18
steliossb wrote:
thanks a lot for the help guys, it was extremely useful.

last question i have for these forums:



This question is already answered here gmatprep-practice-question-probability-coin-77577.html
Manager
Manager
User avatar
Joined: 08 Feb 2009
Posts: 147
Schools: Anderson
Followers: 3

Kudos [?]: 32 [0], given: 3

Re: Three questions from the gmat prep [#permalink] New post 29 May 2009, 12:11
humans wrote:
steliossb wrote:
thanks a lot for the help guys, it was extremely useful.

last question i have for these forums:



This question is already answered here gmatprep-practice-question-probability-coin-77577.html



There is an easier approach/formula for such problems rather than working out all the possible combinations.




If the probability of success in each trial is p, then the probability of r successes in n trials is ^nC_r p^r q^{n-r}


Since, the question asks us to find out probability for at least 4 heads, it gives rise to two scenarios. r = 4 heads exactly or r = 5 heads exactly. And ADD the scenarios finally.


We can infer from the question that probability of heads = p = 0.6, r = 4 or 5, n=5 . Obviously probability for tails = q = 0.4.

Substituting
^5C_4 (0.6)^4 (0.4)^{5-4} + ^5C_5 (0.6)^5 (0.4)^{5-5}

= 5 (0.6)^4 (0.4) + (0.6)^5

Solving the above we get the answer E
Director
Director
avatar
Joined: 23 May 2008
Posts: 840
Followers: 3

Kudos [?]: 32 [0], given: 0

Re: Three questions from the gmat prep [#permalink] New post 29 May 2009, 14:43
vesam wrote:
(1) Prime factor is 2.

4^17 - 2^28 = 2^34 - 2^28 = 2^6 = 64
So 2 is the only prime factor for 64

(2) Answer is C, we can derive the conclusion only with both the statements

(3) Since X < 0, it has to be a -ve number.
If X = -2
So, substitute -2 in the equation
Sqrt (-(-2)|-2|) = Sqrt (2*2) = 2

We took X = -2 and got an answer as 2, so the value will be -X
So I would go for -X, Option A


Thanks,



oops, you're right, should be -x, my bad
Manager
Manager
User avatar
Joined: 13 Jul 2010
Posts: 169
Followers: 1

Kudos [?]: 18 [0], given: 7

Re: Three questions from the gmat prep [#permalink] New post 19 Dec 2010, 15:45
On question 3, I got answer as D as well. sqrt(x*-x) or sqrt(-x^2)=x right? Please advise. thanks.
Expert Post
Math Expert
User avatar
Joined: 02 Sep 2009
Posts: 23519
Followers: 3637

Kudos [?]: 29419 [0], given: 2934

Re: Three questions from the gmat prep [#permalink] New post 19 Dec 2010, 16:06
Expert's post
gettinit wrote:
On question 3, I got answer as D as well. sqrt(x*-x) or sqrt(-x^2)=x right? Please advise. thanks.


The first question: factors-104757.html
The second question: gmat-prep-2-remainder-86155.html
The third question: square-root-and-modulus-100303.html (OA: A)
The fourth question: probability-question-gmatprep-85802.html

Topic locked.
_________________

NEW TO MATH FORUM? PLEASE READ THIS: ALL YOU NEED FOR QUANT!!!

PLEASE READ AND FOLLOW: 11 Rules for Posting!!!

RESOURCES: [GMAT MATH BOOK]; 1. Triangles; 2. Polygons; 3. Coordinate Geometry; 4. Factorials; 5. Circles; 6. Number Theory; 7. Remainders; 8. Overlapping Sets; 9. PDF of Math Book; 10. Remainders; 11. GMAT Prep Software Analysis NEW!!!; 12. SEVEN SAMURAI OF 2012 (BEST DISCUSSIONS) NEW!!!; 12. Tricky questions from previous years. NEW!!!;

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?
25 extra-hard Quant Tests

Get the best GMAT Prep Resources with GMAT Club Premium Membership

Re: Three questions from the gmat prep   [#permalink] 19 Dec 2010, 16:06
    Similar topics Author Replies Last post
Similar
Topics:
Experts publish their posts in the topic Questions from GMAt prep leafsrule99 6 09 Aug 2010, 18:58
from Gmat Prep Question.... gmatJP 0 06 Aug 2014, 11:30
Experts publish their posts in the topic Question from GMAT Prep yeahwill 4 08 Jul 2010, 04:59
Exponent question from GMAT Prep miccarlo 4 03 Aug 2008, 20:54
Function Question from GMAT Prep CFACharterholder22 1 23 Apr 2008, 14:34
Display posts from previous: Sort by

Three questions from the gmat prep

  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®.