BREAKING: Target Test Prep releases Brand New 2026 On Demand GMAT prep course

Redeem

Target Test Prep · GMAT

Choose how you want to prepare

Learn live with an expert or move at your own pace. Every option includes the complete TTP study system.

★★★★★5.0559 reviews
GMATLiveTeach Starts Oct 17
Chris Peckover, Target Test Prep GMAT expert
LIVE ONLINE CLASSES

Get Ready for GMAT Test Day Faster with Live Online Classes

with Chris Peckover, 100th-Percentile GMAT Scorer

Oct 17 · Chris Peckover
Sat · 11:00 AM to 2:00 PM ET
Oct 20 · Chris Peckover
Tue, Thu · 8:00 to 10:00 PM ET
Oct 25 · Josh Braslow
Sun · 1:00 to 4:00 PM ET
Included
40 hours of live online classes + 6 months of TTP OnDemand
  • Attend the first class for free
  • Every class is recorded, so you never fall behind
View classes & enroll
Limited seats availableTarget Test Prep
EALiveTeachOnDemand 5 seats left Start anytime
EXECUTIVE ASSESSMENT

Target Test Prep EA OnDemand

Self-paced EA prep. Study on your schedule.

Logan Thompson
EXECUTIVE ASSESSMENT

Sep 6 to Dec 6, 2026

with Logan Thompson

165+ EA score guarantee
$05-day trial no automatic billing
Schedule
Sun · 9:30 AM to 12:30 PM ET
Included
40 hours of live online classes plus six months of access to the complete TTP EA OnDemand course.
  • 165+ EA Score Guarantee
  • 4,100+ Quant, Verbal, and Integrated Reasoning practice questions
  • 400+ hours of in-depth video lessons
  • 3,000+ step-by-step video solutions
View EA class & enroll Start free 5-day trial
Limited cohort · enrollment openTrial includes full course accessTarget Test Prep
GMATOnDemand Start anytime
SELF-PACED MASTERCLASS

Target Test Prep GMAT OnDemand

Complete access from day one. Study on your schedule.

715+ score guarantee
$0to start then $127/mo
  • Personalized study plan and analytics
  • Thousands of lessons and practice questions
Start free 5-day trial
Read 559 reviewsTarget Test Prep

Compare the format, schedule, and included access before enrolling. Prices and seat counts shown reflect the supplied offer details.

'Average' problem

Problem Solving — algebra and arithmetic (GMAT Focus Edition)
Expert replies
Post new topic Post Reply
Previous Topic Next Topic
Source: — Quantitative Reasoning |
User avatar
Community Manager
Posts: 1060
Joined: Fri May 13, 2011 6:46 amFollowed by: 52 members
Location: Utrecht, The Netherlands
Thanked: 318 times

by neelgandham » Mon Nov 14, 2011 2:49 am
Sam earned a $2,000 commission on a big sale, raising his average commission by $100. If Sam's new average commission is $900, how many sales has he made?

Let total number of sales prior to the big sale be S and
the average commission prior to the big sale be A
Total commission earned prior to the big sale = A*S
Total commission earned after the big sale = A*S + 2000
Total number of sales including the big sale = S+1

Question can be rephrased to What is the value of S+1 ?

900 = Average commission prior to the big sale + 100 = A+100
Implies A = 800

Average commission after the big sale be A = Total commission earned after the big sale/Total number of sales including the big sale
=> (A*S + 2000) / (S+1) = 900
=> (800S + 2000)/(S+1) = 900
=> 800S + 2000 = 900S + 900
=> 100S = 1100
=> S = 11

S+1 = 12 = Total number of sales he made !

p.s: For quick responses,
Please post PS questions here: https://www.beatthegmat.com/problem-solving-f6.html
Please post DS questions here: https://www.beatthegmat.com/data-sufficiency-f7.html
Anil Gandham
Welcome to BEATtheGMAT | Photography | Getting Started | BTG Community rules | MBA Watch
Check out GMAT Prep Now's online course at https://www.gmatprepnow.com/
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
Legendary Member
Posts: 966
Joined: Sat Jan 02, 2010 8:06 amFollowed by: 21 members
Thanked: 230 times

by shankar.ashwin » Mon Nov 14, 2011 3:48 am
You could also do this using allegations.

New commission = Old + 100 = 900.

Old = 800. Resultant = 900 and Addition is 2000. ( 8 and 20 mixed to give 9)

So, (20-9) / (9-8) = 11/1. ( 11 of 8 and 1 of 20)

So, 11 + 1= 12 commissions.
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY

GMAT/MBA Expert

User avatar
GMAT Instructor
Posts: 8207
Joined: Sat Apr 25, 2015 10:56 amFollowed by: 29 members
Location: Los Angeles, CA
Thanked: 43 times

Re: 'Average' problem

by Scott@TargetTestPrep » Tue Sep 08, 2020 9:24 am
Elena89 wrote: ↑
Mon Nov 14, 2011 2:13 am
 Sam earned a $2,000 commission on a big sale, raising his average commission by $100. If Sam's new average commission is $900, how many sales has he made?
Solution:

Since his new average commission is $900, his old average commission must be $800. We can create the equation where n is the number of sales Sam has made before the big sale.

(800n + 2000) / (n + 1) = 900

800n + 2000 = 900n + 900

1100 = 100n

11 = n

Including the big sale, Sam has made 12 sales.

Answer: 12

Scott Woodbury-Stewart
Founder and CEO
[email protected]

Image

See why Target Test Prep is rated 5 out of 5 stars on BEAT the GMAT. Read our reviews

ImageImage
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY

GMAT/MBA Expert

User avatar
GMAT Instructor
Posts: 16207
Joined: Mon Dec 08, 2008 6:26 pmFollowed by: 1268 members
Location: Vancouver, BC
Thanked: 5254 times
GMAT Score:770

Re: 'Average' problem

by Brent@GMATPrepNow » Sat Feb 26, 2022 6:33 am
Elena89 wrote: ↑
Mon Nov 14, 2011 2:13 am
 Sam earned a $2,000 commission on a big sale, raising his average commission by $100. If Sam's new average commission is $900, how many sales has he made?
Note: If Sam's average commission increased by $100 to $900, then his FORMER average commission was $800 and his NEW average commission is $900

When it comes to averages, we know that average value = (sum of n values)/n
We can rewrite this into a useful formula: sum of n values = (average value)(n)

Let n = the number of sales Sam made to calculate his FORMER average commission.
When we apply the above formula, we get: sum of FORMER commissions = 800n

Once Sam collects his $2,000 commission, the NEW sum of commissions = 800n + 2000
At this point, n + 1 = the total number of commissions (since we just added the $2000 commission)

Since Sam's NEW average commission is $900, we can write: 800n + 2000/(n + 1) = $900

Multiply both sides of the equation by (n + 1) to get: 800n + 2000 = 900(n + 1)
Expand the right side: 800n + 2000 = 900n + 900
Subtract 800n from both sides: 2000 = 100n + 900
Subtract 900 from both sides: 1100 = 100n
Solve: n = 11

The question asks us to determine how many sales Sam HAS made, which means we must include the latest sale.
Since n represents the number of sales Sam made to calculate his FORMER average commission, we must add the latest sale (the one that landed Sam a $2,000 commission).
So the total number of sales made = 11 + 1 = 12

Answer: 12
Brent Hanneson - Creator of GMATPrepNow.com
Image
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
Newbie | Next Rank: 10 Posts
Posts: 2
Joined: Sun Jan 02, 2022 11:00 pm

Re: 'Average' problem

by GmatPoint » Thu Jun 02, 2022 1:53 am
New average = $ 900
Since average is increased by $100,
Old average = $ 800

If the total sales were x(before the big sale),
Then, Total commission = $ 800x

By adding the new commission of $ 2000,
Total comission(after the big sale) = $ 800x + 2000

Also, total sales will be x+1.
Thus, $ 2000 + 800x = $ 900(x+1)
100x = 1100
x = 11.

Total sales = x + 1 = 12
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
Senior | Next Rank: 100 Posts
Posts: 30
Joined: Tue Feb 13, 2024 8:47 am

Re: 'Average' problem

by mapadvantageprep » Fri Feb 16, 2024 5:34 am
Given:

Old average commission: $800 (since the new average commission is $100 more than this)
New average commission: $900
Substituting these values into the equation:

x×800+2000=(x+1)×900

Now, let's solve for x:

800x+2000=900x+900
2000=100x+900
1100=100x
x=11

So, Sam made 11 sales before the big sale.

After the big sale, he made 1 additional sale, totaling
x+1=11+1=12 sales.

Therefore, Sam has made 12 sales in total.
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
Post new topic Post Reply
• Page 1 of 1