GMAT Question of the Day - Daily to your Mailbox; hard ones only

It is currently 16 Oct 2019, 07:57

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

Consider a sequence of numbers given by the expression 7 + (n - 1) * 5

  new topic post reply Question banks Downloads My Bookmarks Reviews Important topics  
Author Message
TAGS:

Hide Tags

Find Similar Topics 
Manager
Manager
User avatar
Joined: 20 Jan 2014
Posts: 139
Location: India
Concentration: Technology, Marketing
GMAT ToolKit User
Consider a sequence of numbers given by the expression 7 + (n - 1) * 5  [#permalink]

Show Tags

New post 06 Oct 2014, 23:37
1
7
00:00
A
B
C
D
E

Difficulty:

  25% (medium)

Question Stats:

82% (02:20) correct 18% (02:40) wrong based on 121 sessions

HideShow timer Statistics

Consider a sequence of numbers given by the expression 7 + (n - 1) * 5, where n runs from 1 to 80.What is the sum of this series ?

A. 409
B. 1636
C. 16360
D. 16000
E. 15360

_________________
Consider +1 Kudos Please :)
Senior Manager
Senior Manager
User avatar
Joined: 13 Jun 2013
Posts: 266
Re: Consider a sequence of numbers given by the expression 7 + (n - 1) * 5  [#permalink]

Show Tags

New post 07 Oct 2014, 00:08
2
him1985 wrote:
Consider a sequence of numbers given by the expression 7 + (n - 1) * 5, where n runs from 1 to 80.What is the sum of this series ?

A. 409
B. 1636
C. 16360
D. 16000
E. 15360


terms in this sequence are 7,12,17----402

now since this is an a.p. with a common difference of 5. therefore its sum can be given as
n(a+l)/2----------------1)

n= total no. of terms =80
a= first term=7
l= last term=402

subsitutuing values in the expression 1 we have

80(7+402)/2
= 40(409)
=16360
Director
Director
User avatar
S
Status: Come! Fall in Love with Learning!
Joined: 05 Jan 2017
Posts: 532
Location: India
Re: Consider a sequence of numbers given by the expression 7 + (n - 1) * 5  [#permalink]

Show Tags

New post 27 Feb 2017, 06:38
n = 80
a = 7
d = 5
Sum = {n( first term + last term)}/2
= {80( 7 + 7 + 79*5)}/2
= 16360. Option C
_________________
GMAT Mentors
Image
Target Test Prep Representative
User avatar
G
Status: Head GMAT Instructor
Affiliations: Target Test Prep
Joined: 04 Mar 2011
Posts: 2816
Re: Consider a sequence of numbers given by the expression 7 + (n - 1) * 5  [#permalink]

Show Tags

New post 01 Mar 2017, 18:17
him1985 wrote:
Consider a sequence of numbers given by the expression 7 + (n - 1) * 5, where n runs from 1 to 80.What is the sum of this series ?

A. 409
B. 1636
C. 16360
D. 16000
E. 15360


We are given the sequence 7 + (n - 1) * 5, in which n spans from 1 to 80. Let’s determine the first few values of the sequence.

n = 1

7 + (0 x 5) = 7

n = 2

7 + (1 x 5) = 12

n = 3

7 + (2 x 5) = 17

n = 4

7 + (3 x 5 ) = 22

We see that we have an evenly spaced set in which each term is 5 apart. To determine the sum, we can use the formula: sum = average x quantity. Since we know the quantity is 80, we need to determine the average.

We can use the formula: average = (first term in the set + last term in the set)/2

The last term in the set is 7 + (79 x 5) = 402, and thus:

average = (7 + 402)/2 = 409/2

Now we can calculate the sum:

sum = (409/2) x 80 = 16,360

Answer: C
_________________

Jeffrey Miller

Head of GMAT Instruction

Jeff@TargetTestPrep.com
TTP - Target Test Prep Logo
122 Reviews

5-star rated online GMAT quant
self study course

See why Target Test Prep is the top rated GMAT quant course on GMAT Club. Read Our Reviews

If you find one of my posts helpful, please take a moment to click on the "Kudos" button.

Director
Director
avatar
S
Joined: 12 Nov 2016
Posts: 701
Location: United States
Schools: Yale '18
GMAT 1: 650 Q43 V37
GRE 1: Q157 V158
GPA: 2.66
Re: Consider a sequence of numbers given by the expression 7 + (n - 1) * 5  [#permalink]

Show Tags

New post 16 Mar 2017, 13:33
manpreetsingh86 wrote:
him1985 wrote:
Consider a sequence of numbers given by the expression 7 + (n - 1) * 5, where n runs from 1 to 80.What is the sum of this series ?

A. 409
B. 1636
C. 16360
D. 16000
E. 15360


terms in this sequence are 7,12,17----402

now since this is an a.p. with a common difference of 5. therefore its sum can be given as
n(a+l)/2----------------1)

n= total no. of terms =80
a= first term=7
l= last term=402

subsitutuing values in the expression 1 we have

80(7+402)/2
= 40(409)
=16360


Kudos for the formula- I wanted to ask you- I see similar series problems on Veritasprep and wanted to ask if this formula is universal (I think it is). I have never seen this formula but now it makes a lot of sense- where did you get this formula from?
Non-Human User
User avatar
Joined: 09 Sep 2013
Posts: 13199
Re: Consider a sequence of numbers given by the expression 7 + (n - 1) * 5  [#permalink]

Show Tags

New post 25 Jan 2019, 07:51
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 Club Bot
Re: Consider a sequence of numbers given by the expression 7 + (n - 1) * 5   [#permalink] 25 Jan 2019, 07:51
Display posts from previous: Sort by

Consider a sequence of numbers given by the expression 7 + (n - 1) * 5

  new topic post reply Question banks Downloads My Bookmarks Reviews Important topics  





Powered by phpBB © phpBB Group | Emoji artwork provided by EmojiOne