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

Redeem

Matt needs help!

This topic has expert replies
Post new topic Post Reply
Previous Topic Next Topic
User avatar
Junior | Next Rank: 30 Posts
Posts: 24
Joined: Tue Mar 06, 2012 5:35 am

Matt needs help!

by rrobiinn » Mon Aug 13, 2012 11:10 pm
Matt gets a $1,000 commission on a big sale.This commission alone raises his aver-age commission by $150.If Matt's new average commission is $400,how many sales has Matt made?

- I found the solution like this:

"s=total number of things sold (before big sale)
x=number of things sold (before big sale)

so s/x = 250
s = 250x

after big sale

(s+1000)/(x+1) = 400

s+1000 = 400x+400

since s = 250x

250x+1000 = 400x+400

150x = 600

x= 4

so after the big commision, sales are x+1 = 4+1 = 5"

I don't understand why it is (x+1), meaning the sales has increased by 1, after the big sale. how come (x+1) !
Top
Source: — Problem Solving |
User avatar
Master | Next Rank: 500 Posts
Posts: 210
Joined: Thu Mar 08, 2012 11:24 pm
Thanked: 62 times
Followed by:3 members

by niketdoshi123 » Mon Aug 13, 2012 11:24 pm
rrobiinn wrote:Matt gets a $1,000 commission on a big sale.This commission alone raises his aver-age commission by $150.If Matt's new average commission is $400,how many sales has Matt made?

- I found the solution like this:

"s=total number of things sold (before big sale) It should be total commission on the previous sales.
x=number of things sold (before big sale)

so s/x = 250
s = 250x

after big sale

(s+1000)/(x+1) = 400

s+1000 = 400x+400

since s = 250x

250x+1000 = 400x+400

150x = 600

x= 4

so after the big commision, sales are x+1 = 4+1 = 5"

I don't understand why it is (x+1), meaning the sales has increased by 1, after the big sale. how come (x+1) !
a big sale = 1 sale
x = # of sales before the big sale
=> total # of sales after the big sale = x+1
Top
User avatar
GMAT Instructor
Posts: 15539
Joined: Tue May 25, 2010 12:04 pm
Location: New York, NY
Thanked: 13060 times
Followed by:1906 members
GMAT Score:790

by GMATGuruNY » Tue Aug 14, 2012 2:01 am
rrobiinn wrote:Matt gets a $1,000 commission on a big sale.This commission alone raises his aver-age commission by $150.If Matt's new average commission is $400,how many sales has Matt made?
Old sum before the sale = (old number of sales)(old average) = x(250) = 250x.
New sum after the big sale = (new number of sales)(new average) = (x+1)400 = 400x + 400.
Since the new sum is 1000 greater than the old sum:
400x + 400 = 250x + 1000
150x = 600
x = 4.
New number of sales = x+1 = 4+1 = 5.

When taking the GMAT, we could plug in the answer choices, which would represent the number of sales AFTER the big sale.
When the correct answer is plugged in, the difference between the new sum (at an average of 400 per sale) and the old sum (at an average of 250 per sale) must be 1000.
Given the following answer choices:

2
3
4
5
6

Answer choice C: 4
New sum - old sum = 4(400) - 3(250) = 850.
Too small.
Eliminate A, B and C.

Answer choice D: 5
New sum - old sum = 5(400) - 4(250) = 1000.
Success!

The correct answer is D.
Private tutor exclusively for the GMAT and GRE, with over 20 years of experience.
Followed here and elsewhere by over 1900 test-takers.
I have worked with students based in the US, Australia, Taiwan, China, Tajikistan, Kuwait, Saudi Arabia -- a long list of countries.
My students have been admitted to HBS, CBS, Tuck, Yale, Stern, Fuqua -- a long list of top programs.

As a tutor, I don't simply teach you how I would approach problems.
I unlock the best way for YOU to solve problems.

For more information, please email me (Mitch Hunt) at [email protected].
Student Review #1
Student Review #2
Student Review #3
Top
Post new topic Post Reply
• Page 1 of 1