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

 It is currently 05 May 2015, 14:06

### 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

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

# Events & Promotions

###### Events & Promotions in June
Open Detailed Calendar

# PS;: SUM

Author Message
TAGS:
Senior Manager
Joined: 02 Feb 2004
Posts: 345
Followers: 1

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

PS;: SUM [#permalink]  15 Apr 2005, 06:52
00:00

Difficulty:

(N/A)

Question Stats:

0% (00:00) correct 0% (00:00) wrong based on 0 sessions
PLZ EXPLAIN
Attachments

0031.jpg [ 7.56 KiB | Viewed 534 times ]

Director
Joined: 18 Feb 2005
Posts: 674
Followers: 1

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

Re: PS;: SUM [#permalink]  15 Apr 2005, 08:48
mirhaque wrote:
PLZ EXPLAIN

13 is the 7th term and 39 is the 20th term

Now we have sum of n terms is n^2

So take a difference of the squares of poisitions of 39 and 13 which is
400-49 = 351
VP
Joined: 25 Nov 2004
Posts: 1495
Followers: 6

Kudos [?]: 38 [0], given: 0

Re: PS;: SUM [#permalink]  16 Apr 2005, 16:06
gmat2me2 wrote:
13 is the 7th term and 39 is the 20th term
Now we have sum of n terms is n^2. So take a difference of the squares of poisitions of 39 and 13 which is 400-49 = 351

gmat2me2, you have right approach. but you overlooked and miscalculated. it says including 13 and 39. it should be =20^2-6^2=364.

or alternatively, sum = n(F+L)/2 = 14(13+39)/2 = 14x26=364
Director
Joined: 18 Feb 2005
Posts: 674
Followers: 1

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

Re: PS;: SUM [#permalink]  16 Apr 2005, 18:43
MA wrote:
gmat2me2 wrote:
13 is the 7th term and 39 is the 20th term
Now we have sum of n terms is n^2. So take a difference of the squares of poisitions of 39 and 13 which is 400-49 = 351

gmat2me2, you have right approach. but you overlooked and miscalculated. it says including 13 and 39. it should be =20^2-6^2=364.

or alternatively, sum = n(F+L)/2 = 14(13+39)/2 = 14x26=364

This is what I am afraid of...... I try to do very quickly and landup making silly mistakes.......I should improve my strike rate

Thanks though for the catch
Re: PS;: SUM   [#permalink] 16 Apr 2005, 18:43
Similar topics Replies Last post
Similar
Topics:
PS: Sum 6 16 Nov 2008, 08:45
PS - sum of factorials 9 28 Apr 2007, 04:08
ps:sum 4 26 May 2006, 13:08
ps:sum 1 27 Mar 2006, 14:41
ps - sum + sum ? 7 20 Oct 2005, 11:31
Display posts from previous: Sort by