It is currently 11 Dec 2017, 14:08

### 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

# Events & Promotions

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

# What is the sum of all consecutive integers from 10 to 100, inclusive?

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

### Hide Tags

Math Expert
Joined: 02 Sep 2009
Posts: 42544

Kudos [?]: 135259 [0], given: 12679

What is the sum of all consecutive integers from 10 to 100, inclusive? [#permalink]

### Show Tags

18 Oct 2016, 02:11
Expert's post
2
This post was
BOOKMARKED
00:00

Difficulty:

15% (low)

Question Stats:

77% (00:44) correct 23% (01:01) wrong based on 117 sessions

### HideShow timer Statistics

What is the sum of all consecutive integers from 10 to 100, inclusive?

A. 4550
B. 4950
C. 5005
D. 5500
E. 5555
[Reveal] Spoiler: OA

_________________

Kudos [?]: 135259 [0], given: 12679

Intern
Status: reappearing for gmat
Joined: 10 Jul 2016
Posts: 41

Kudos [?]: 102 [0], given: 40

Location: India
Concentration: Entrepreneurship, Finance
GPA: 3.78
Re: What is the sum of all consecutive integers from 10 to 100, inclusive? [#permalink]

### Show Tags

18 Oct 2016, 02:31
3
This post was
BOOKMARKED
Bunuel wrote:
What is the sum of all consecutive integers from 10 to 100, inclusive?

A. 4550
B. 4950
C. 5005
D. 5500
E. 5555

This question can be solved in many ways.

But using this formula, you can calculate the answer in seconds

SUM= n/2(Starting number+ Ending number)

n: total numbers between the starting no. and ending no.

n= 100-10+1= 91

SUM= (91/2)*(10+100)
= 91*55
=5005

Hence, answer C
_________________

go with the flow

KUDOS +1 if you like the post

Kudos [?]: 102 [0], given: 40

Manager
Joined: 28 Jun 2016
Posts: 207

Kudos [?]: 92 [0], given: 63

Location: Canada
Concentration: Operations, Entrepreneurship
Re: What is the sum of all consecutive integers from 10 to 100, inclusive? [#permalink]

### Show Tags

18 Oct 2016, 02:32
1
This post was
BOOKMARKED
Sum of 1st 100 integers=100*101/2 = 5050

Sum of 1st 9 integers = 9*10/2 = 45

Answer = 5050-45 = 5005

C

Sent from my iPhone using GMAT Club Forum mobile app

Kudos [?]: 92 [0], given: 63

Retired Moderator
Joined: 26 Nov 2012
Posts: 594

Kudos [?]: 180 [0], given: 45

Re: What is the sum of all consecutive integers from 10 to 100, inclusive? [#permalink]

### Show Tags

18 Oct 2016, 02:56
Bunuel wrote:
What is the sum of all consecutive integers from 10 to 100, inclusive?

A. 4550
B. 4950
C. 5005
D. 5500
E. 5555

Total numbers from 10 to 100 will be 100-10+1 = 91.

Since the numbers are consecutive then we'll get difference as 1 between any two numbers.. So this is Arithematic progression.

Sn = n/2(first number + last number) => 91/2(10+100) => 5005

IMO option C.

Kudos [?]: 180 [0], given: 45

Board of Directors
Status: QA & VA Forum Moderator
Joined: 11 Jun 2011
Posts: 3105

Kudos [?]: 1142 [0], given: 327

Location: India
GPA: 3.5
WE: Business Development (Commercial Banking)
What is the sum of all consecutive integers from 10 to 100, inclusive? [#permalink]

### Show Tags

18 Oct 2016, 03:31
Bunuel wrote:
What is the sum of all consecutive integers from 10 to 100, inclusive?

A. 4550
B. 4950
C. 5005
D. 5500
E. 5555

 Sum of all consecutive integers from 10 to 100 = Sum of all consecutive integers up to 100 - Sum of all consecutive integers up to 9

Sum of all consecutive integers from 10 to 100 = $$100*\frac{101}{2}$$ - $$9*\frac{10}{2}$$

Sum of all consecutive integers from 10 to 100 = $$5050$$ - $$45$$

Sum of all consecutive integers from 10 to 100 = $$5005$$

Hence correct answer will be (C)....
_________________

Thanks and Regards

Abhishek....

PLEASE FOLLOW THE RULES FOR POSTING IN QA AND VA FORUM AND USE SEARCH FUNCTION BEFORE POSTING NEW QUESTIONS

How to use Search Function in GMAT Club | Rules for Posting in QA forum | Writing Mathematical Formulas |Rules for Posting in VA forum | Request Expert's Reply ( VA Forum Only )

Kudos [?]: 1142 [0], given: 327

Manager
Joined: 29 Aug 2008
Posts: 111

Kudos [?]: 50 [0], given: 284

Re: What is the sum of all consecutive integers from 10 to 100, inclusive? [#permalink]

### Show Tags

19 Oct 2016, 01:56
Sum of first n consecutive integers = n*(n+1)/2

Sum of 100 consecutive integers = 100*101/2

Sum of first 9 integers (we have to find sum of 10 to 100 inclusive, so we have to consider till 9 only) = 9*10/2

100*101/2 - 9*10/2

= 5005

Option C.

Kudos [?]: 50 [0], given: 284

Intern
Joined: 17 Jan 2014
Posts: 10

Kudos [?]: 2 [0], given: 11

Re: What is the sum of all consecutive integers from 10 to 100, inclusive? [#permalink]

### Show Tags

23 Oct 2016, 03:44
Bunuel wrote:
What is the sum of all consecutive integers from 10 to 100, inclusive?

A. 4550
B. 4950
C. 5005
D. 5500
E. 5555

It is an arithmetic progression with the first term being 10 and the last term being 100

Sum= n/2(2a + (n-1)d)

N being the no. of terms equals 91 (90 numbers from 11 to 100. 10 being additional one as it is inclusive)

Sum = 91/2(10*2 + (91-1)*1)
=5005

Answer = Option C

Sent from my Le X526 using Tapatalk

Kudos [?]: 2 [0], given: 11

Target Test Prep Representative
Status: Founder & CEO
Affiliations: Target Test Prep
Joined: 14 Oct 2015
Posts: 1922

Kudos [?]: 1010 [1], given: 3

Location: United States (CA)
Re: What is the sum of all consecutive integers from 10 to 100, inclusive? [#permalink]

### Show Tags

24 Oct 2016, 18:36
1
This post received
KUDOS
Expert's post
Bunuel wrote:
What is the sum of all consecutive integers from 10 to 100, inclusive?

A. 4550
B. 4950
C. 5005
D. 5500
E. 5555

We know that the general average formula is average = sum/quantity. This formula can be rearranged to isolate the sum of the values in the set: sum = average x quantity. This tells us that the sum of any set of numbers is equal to the number of terms in the set multiplied by the average of the numbers in the set.

Let’s start by determining how many terms are in the set.

quantity = 100 - 10 + 1 = 91

Next we can determine the average of the numbers from 10 to 100, inclusive. Since we are dealing with consecutive integers, which form an evenly spaced set of numbers, we can use the following formula to determine the average:

average = (1st number + last number)/2

average = (10 + 100)/2 = 110/2 = 55

Now, the sum can be calculated by means of the rearranged formula:

sum = 55 x 91 = 5,005

Answer: C
_________________

Scott Woodbury-Stewart
Founder and CEO

GMAT Quant Self-Study Course
500+ lessons 3000+ practice problems 800+ HD solutions

Kudos [?]: 1010 [1], given: 3

Senior Manager
Status: DONE!
Joined: 05 Sep 2016
Posts: 408

Kudos [?]: 26 [0], given: 283

Re: What is the sum of all consecutive integers from 10 to 100, inclusive? [#permalink]

### Show Tags

26 Oct 2016, 19:16
Question can be solved using: sum/# = avg

#: 100-10+1 = 91
avg: we know that there are 91 numbers and the avg will occur at 91/2 = 45....rounded up to 46 --> 46th number in the lineup will be the avg. To find what number that is: x-10+1 = 46--> x = 55

Thus..the equation can be transformed into the following: SUM/91 = 55 --> SUM = 5005

Hence, C is correct.

Kudos [?]: 26 [0], given: 283

Intern
Joined: 11 Oct 2017
Posts: 22

Kudos [?]: 6 [0], given: 82

Re: What is the sum of all consecutive integers from 10 to 100, inclusive? [#permalink]

### Show Tags

12 Oct 2017, 13:05
1
This post was
BOOKMARKED
This is how I've been getting them right. Idk if this is the most efficient way though.

N for consecutive numbers = (First Number - Last Number) +1

Sum of numbers = (First Number + Last Number) * N))/2

1. (100-10) +1 = 91

2. (100+10)*91))/2 = 5005 C

Kudos [?]: 6 [0], given: 82

Re: What is the sum of all consecutive integers from 10 to 100, inclusive?   [#permalink] 12 Oct 2017, 13:05
Display posts from previous: Sort by

# What is the sum of all consecutive integers from 10 to 100, inclusive?

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

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