Last visit was: 26 Apr 2026, 23:14

It is currently 26 Apr 2026, 23:14

Toolkit

Practice Tests

Data Insights Questions

Data Sufficiency (DS)

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.

Go to My Error Log Learn more

Request Expert Reply

Confirm Cancel

Apr 27
Try OnDemand GMAT Masterclass
11:00 AM EDT
-
12:00 PM EDT
Prefer video-based learning? The Target Test Prep OnDemand course is a one-of-a-kind video masterclass featuring 400 hours of lecture-style teaching by Scott Woodbury-Stewart, founder of Target Test Prep and one of the most accomplished GMAT instructors
Apr 26
Score High on the GMAT with Target Test Prep
10:00 AM EDT
-
11:00 AM EDT
The Target Test Prep course represents a quantum leap forward in GMAT preparation, a radical reinterpretation of the way that students should study. Try before you buy with a 5-day, full-access trial of the course for FREE!
Apr 28
Join - GMAT Day!
08:00 AM PDT
-
11:00 AM PDT
Whether you are just beginning your MBA journey or fine-tuning your path to a 700+ score, GMAT Day is designed to give you a competitive edge.

Back to Forum

Create Topic

How many integers are there between, but not including, integers r and

1 2

AliciaSierra

Joined: 17 Mar 2014

Last visit: 14 Jun 2024

Posts: 736

Own Kudos:

648

[2]

Given Kudos: 1,350

Products:

Posts: 736

Kudos: 648

[2]

15 May 2018, 10:16

Kudos

Bookmarks

Why did we assume that R to S is continuous series ?

can't it be 0, 1, 10

R=0, S=10 ..but number of integer between S and R will 1.

amanvermagmat

Retired Moderator

Joined: 22 Aug 2013

Last visit: 28 Mar 2025

Posts: 1,142

Own Kudos:

2,973

Given Kudos: 480

Location: India

Posts: 1,142

Kudos: 2,973

15 May 2018, 10:49

Kudos

Bookmarks

ammuseeru

Why did we assume that R to S is continuous series ?

can't it be 0, 1, 10

R=0, S=10 ..but number of integer between S and R will 1.

Hello

What do you mean by continuous series - can you please make it clear?
Whichever values we assume for r/s, as far as those values satisfy the given constraint (that s - r = 10), there will always be 9 integers between them.

The values that you have taken: r=0, s=10 - here also there are 9 integers between r and s (1, 2, 3, 4, 5, 6, 7, 8, 9).

stne

Joined: 27 May 2012

Last visit: 26 Apr 2026

Posts: 1,811

Own Kudos:

2,093

[2]

Given Kudos: 681

Posts: 1,811

Kudos: 2,093

[2]

06 Feb 2019, 23:29

Kudos

Bookmarks

dzodzo85

How many integers are there between, but not including, integers r and s ?

(1) s – r = 10
(2) There are 9 integers between, but not including, r + 1 and s + 1.

I may have mistakenly chosen the wrong answer, but nevertheless some expert explanation will help me understand this better.

Dear Moderator,
Found this DS question in the PS section, hope you will do the needful. Thank you.

Bunuel

Math Expert

Joined: 02 Sep 2009

Last visit: 26 Apr 2026

Posts: 109,921

Own Kudos:

811,474

Given Kudos: 105,908

Products:

Expert

Expert reply

Posts: 109,921

Kudos: 811,474

06 Feb 2019, 23:53

Kudos

Bookmarks

stne

dzodzo85

Dear Moderator,
Found this DS question in the PS section, hope you will do the needful. Thank you.

__________________
Merged. Thank you.

BrentGMATPrepNow

Major Poster

Joined: 12 Sep 2015

Last visit: 31 Oct 2025

Posts: 6,733

Own Kudos:

36,471

[3]

Given Kudos: 799

Location: Canada

Expert

Expert reply

Posts: 6,733

Kudos: 36,471

[3]

10 Feb 2020, 08:57

Kudos

Bookmarks

Bunuel

How many integers are there between, but not including, integers r and s ?

(1) s - r = 10
(2) There are 9 integers between, but not including, r + 1 and s + 1.

Target question: How many integers are there between, but not including, integers r and s ?

Statement 1: s - r = 10
First of all, this tells us that s is greater than r
So, on the number line, we have: ------r------------s----

Also notice that, if we take the given equation and add r to both sides, we get s = r+10
So, we can replace s with r+10 to get: ------r------------(r+10)----

Since r is an integer, we know that r+1 is an integer, and r+2 is an integer, and r+3 is an integer, etc.
If we add all of these values to our number line we get: ------r--(r+1)--(r+2)--(r+3)--(r+4)--(r+5)--(r+6)--(r+7)--(r+8)--(r+9)--(r+10)----
We can see that there are 9 integers between r and s
Since we can answer the target question with certainty, statement 1 is SUFFICIENT

Statement 2: There are 9 integers between, but not including, r + 1 and s + 1.
The key here is to recognize that the number of integers between r + 1 and s + 1 IS THE SAME AS the number of integers between r and s

For example, we know that there are three integers between 5 and 9 (the integers are 6, 7 and 8)
If we add one to 5 and 9, we get 6 and 10
Notice that there are also three integers between 6 and 10 (the integers are 7, 8 and 9)

So, if there are 9 integers between r + 1 and s + 1, then we can also conclude that there are 9 integers between r and s
Since we can answer the target question with certainty, statement 2 is SUFFICIENT

Answer: D

Cheers,
Brent

TheUltimateWinner

Joined: 23 Feb 2015

Last visit: 16 Apr 2026

Posts: 2,465

Own Kudos:

2,460

Given Kudos: 1,990

Concentration: Finance, Technology

Schools: Harvard '24 Judge '23 LBS '24 McCombs '24 Mendoza Tepper '24 Ross '24 Cox Marshall '24 Fisher Kelley '24 Jones McDonough '24 Owen '24 Terry BU Simon '24 Katz GWU Mason Babson Gabelli Foster '24 Goizueta '24 Scheller Stern '23 CBS '23 Booth '23 Haas '25 Wharton '25 Stanford '26 Johnson'23 Fuqua '23 Kellogg '23 Kenan-Flagler'23 INSEAD Aug 22 intake Olin '23 Said '23 Sloan '23 Carey Arizona "22 Yale '23 UC Davis Madison '23 Anderson '23 Carroll Carlson '23 Darden '23

Posts: 2,465

Kudos: 2,460

21 Feb 2020, 13:38

Kudos

Bookmarks

longhaul123

one small doubt in the statement 1. Why shouldn't we consider s=-10 and r=20 in which case the sum is 10 but the number of integers between them is not 9. Kindly explain

If s=-10 and r=-20 then it makes sense. s-r=10 and the integers between s and r is also 9.
Hope it helps.

TheUltimateWinner

Joined: 23 Feb 2015

Last visit: 16 Apr 2026

Posts: 2,465

Own Kudos:

2,460

Given Kudos: 1,990

Concentration: Finance, Technology

Posts: 2,465

Kudos: 2,460

21 Feb 2020, 13:58

Kudos

Bookmarks

ammuseeru

Why did we assume that R to S is continuous series ?

can't it be 0, 1, 10

R=0, S=10 ..but number of integer between S and R will 1.

Hello ammuseeru

Quote:

How many integers are there between, but not including, integers r and s ?

(1) s - r = 10
(2) There are 9 integers between, but not including, r + 1 and s + 1.

You can consider whatever you like in the highlighted part until you consider both statements. But, if you take statement 1 then you have to be specific in your thinking.
In statement 1, s-r=10 means s=r+10.

r--(r+1)---(r+2)---(r+3)----(r+4)---(r+5)---(r+6)---(r+7)---(r+8)--(r+9)----s (r+10)-->The are just 9 integers.
So, it has to be in ''continuous serious'' definitely.
If you're asked that how many integers between 97 and 100? can you skip any digit? definitely not. The series are continuous (97, 98, 99, 100).

Quote:

R=0, S=10 ..but number of integer between S and R will 1

Here, the number of integers=(s-r)+1
=10+1 (in statement 1, s-r=10)
=11
=11-2(excluding s and r)
=9 integers
Hope it helps.

totaltestprepNick

Joined: 25 Aug 2014

Last visit: 26 Apr 2026

Posts: 469

Own Kudos:

Given Kudos: 2

GMAT 1: 750 Q49 V42 Verified score

Posts: 469

Kudos: 4

04 Mar 2026, 11:31

Kudos

Bookmarks

Bunuel

How many integers are there between, but not including, integers r and s ?

(1) s-r=10
(2) There are 9 integers between, but not including, r + 1 and s + 1.

Show Spoiler