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

It is currently 25 Oct 2014, 11:56

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

The sum of the first n positive perfect squares, where n is

  Question banks Downloads My Bookmarks Reviews Important topics  
Author Message
TAGS:
Manager
Manager
avatar
Joined: 20 Jun 2012
Posts: 96
Location: United States
Concentration: Finance, Operations
GMAT 1: 650 Q50 V28
GMAT 2: 700 Q50 V35
Followers: 1

Kudos [?]: 23 [0], given: 42

GMAT ToolKit User
Re: The sum of the first n positive perfect squares, where n is [#permalink] New post 12 Jun 2013, 04:15
Bunuel wrote:
stunn3r wrote:
kirankp wrote:
The sum of the first n positive perfect squares, where n is a positive integer, is given by the formula \frac{n^3}{3} + c*n^2 + \frac{n}{6}, where c is a constant. What is the sum of the first 15 positive perfect squares?

(A) 1,010
(B) 1,164
(C) 1,240
(D) 1,316
(E) 1,476


First of all there is a direct formula also provided above by bunuel i.e. [(n)(n+1)(2n+1)]/6

now if we do not know this and directly put 15 in place of N ..

It'll come >> 15[225/3+15c+1/6] = 15[(451+90c)/6] = 5[(451 + 90c)/2] ..

now (450 + 90c) should be an even integer so that it should get divisible by 2, that figured out c has to be in fraction and as (450 + 90c) is an even integer answer should have "0" in the last(because it'll be multiplied by "5" outside [ ] ) .. we can eliminate B,D,E ryt away ..

for choosing between A and C. I took 1/2 as my first no. and bingo I got the answer :D


Note that OA is C, not D. Check here: the-sum-of-the-first-n-positive-perfect-squares-where-n-is-90497.html#p831532

Hope it helps.


hahahahaha .. that was the funnies confusion .. I guess you are not much into texting that ":D" was a smiley like this >> :-D
_________________

Forget Kudos ... be an altruist

Kaplan Promo CodeKnewton GMAT Discount CodesManhattan GMAT Discount Codes
Manager
Manager
avatar
Joined: 03 Mar 2013
Posts: 91
Location: India
Concentration: General Management, Marketing
GPA: 3.49
WE: Web Development (Computer Software)
Followers: 0

Kudos [?]: 7 [0], given: 6

Re: The sum of the first n positive perfect squares, where n is [#permalink] New post 03 Jul 2013, 09:30
kirankp wrote:
The sum of the first n positive perfect squares, where n is a positive integer, is given by the formula \frac{n^3}{3} + c*n^2 + \frac{n}{6}, where c is a constant. What is the sum of the first 15 positive perfect squares?

(A) 1,010
(B) 1,164
(C) 1,240
(D) 1,316
(E) 1,476



traditional way: put n = 1 and find c and then now substitute 15

but if u know the formula for sum of squares of n natural number (n) x (n+1 )x (2n+1 )/ 6
now directly keep n - 15 :)
CEO
CEO
User avatar
Joined: 09 Sep 2013
Posts: 2869
Followers: 208

Kudos [?]: 43 [0], given: 0

Premium Member
Re: The sum of the first n positive perfect squares, where n is [#permalink] New post 09 Jul 2014, 01:44
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

Re: The sum of the first n positive perfect squares, where n is   [#permalink] 09 Jul 2014, 01:44
    Similar topics Author Replies Last post
Similar
Topics:
2 Experts publish their posts in the topic The sum of the first n positive perfect squares, where n is carcass 6 17 May 2012, 12:43
11 Experts publish their posts in the topic Is the positive integer N a perfect square? netcaesar 17 13 Aug 2009, 05:49
What is the sum of the squares of the first n positive HVD1975 5 30 Aug 2008, 11:09
what is the sum of the squares of the first n positive el1981 4 06 Mar 2008, 19:03
What is the sum of the square of the first n positive mdf2 3 26 Jan 2005, 22:11
Display posts from previous: Sort by

The sum of the first n positive perfect squares, where n is

  Question banks Downloads My Bookmarks Reviews Important topics  

Go to page   Previous    1   2   [ 23 posts ] 



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®.