by: hujumen
8 mins
Events & Promotions
|
|
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
Track
Your Progress
Practice
Pays
Not interested in getting valuable practice questions and articles delivered to your email? No problem, unsubscribe here.
Sep 0201:00 PM EDT
-11:59 PM EDT
Take 30% off all study plans with code COURSEWORK - Expires on Monday 9/7
Sep 0410:00 AM EDT
-11:59 PM EDT
We’ve worked incredibly hard to build TTP into the best test prep experience possible, and it would mean a lot to us to win Newsweek’s 2026 Readers’ Choice Award for Best Test Prep. If TTP has helped you, we’d be incredibly grateful for your vote.
Sep 0609:30 AM EDT
-12:30 PM EST
Top scores are possible when you enroll in a powerful EA course, taught live online + 6 months access to TTP OnDemand video courses included! Perfect class schedule and easy course access for working professionals. Class starts Sundays Sept. 6, 2026.
Sep 0712:01 AM PDT
-11:59 PM PDT
On the 7th, GMAT Club Tests will be Free! Including all the Quizzes, Questions, and Tests. 12 AM - 11:59 PM PDT- Sep 07
10:00 AM PDT
-11:00 AM PDT
A complete walkthrough of GMAT Club’s free 12-week GMAT study plan: what you study each week, how progress and goals are tracked, how the error log works, and how your practice unlocks paid tools at no cost. - Sep 09
07:00 AM PDT
-10:00 AM PDT
Meet AdComs and explore top Master’s programs - MiM, MiF, MSc, MSBA and more. - Application Fee Waivers - Free 1-Week of GMAT Club Tests: - Master's Application Toolkit - Grand Prize Giveaway - Sep 09
10:00 AM PDT
-11:00 AM PDT
Three MBA applications. Three rejections. No interview invites. A year later, Aman was admitted to Cambridge Judge, SMU, and IMD. In this episode of MBA Admit Stories, Aman shares how he rebuilt his MBA application... 
Sep 1507:00 PM EDT
-09:00 PM EST
Elite scores are possible when you enroll in a powerful GMAT course, taught live online + 6 months access to TTP OnDemand video courses included! Class starts Tues/Thurs Sept. 15, 2026 - Nov. 15, 2027, 7:00pm-9:00pm EST
Sep 2108:00 PM EDT
-10:00 PM EDT
Boost your GMAT score in less than one month in a live online class + 6 months access to TTP OnDemand video courses included! Class starts Mon, Tues, Wed, Thur, Fri Sept. 21, 2026 - Oct. 9, 2027, 7:00pm-10:00pm EST
Be sure to select an answer first to save it in the Error Log before revealing the correct answer (OA)!
Difficulty:
75%
(hard)
Question Stats:
75% (03:23) correct
25%
(03:49)
wrong
based on 1688
sessions
History
Date
Time
Result
Not Attempted Yet
A company purchased at least 10 units of a certain product from each of Suppliers X and Y. Supplier X charged a $100 fixed cost, $20 per unit for each of the first 10 units, and $5 per unit for each unit purchased in excess of 10 units. Supplier Y charged a $150 fixed cost, $15 per unit for each of the first 10 units, and $10 per unit for each unit purchased in excess of 10 units. Including the fixed costs, the combined average cost for the units was $20 per unit.
Select a number of units purchased from Supplier X and a number of units purchased from Supplier Y that are jointly consistent with the given information. Make only two selections, one in each column.
Select a number of units purchased from Supplier X and a number of units purchased from Supplier Y that are jointly consistent with the given information. Make only two selections, one in each column.
|
Number of units purchased from Supplier X |
Number of units purchased from Supplier Y |
|
| 15 | ||
| 20 | ||
| 22 | ||
| 25 | ||
| 27 | ||
| 30 |
ID: 700233
Every tricky question should trigger a follow up quiz.
Build that habit with
GMAT Club Forum Quiz →.
Atleast 10 units from each product means min. 10 products of X and 10 products of Y.
Cost = Fixed cost + Cost of first 10 products + Cost of remaining products.
For X,
Cost = 100 + 20x10 + 5 (X-10) ----[1]
For Y,
Cost = 150 + 10x10 + 10 (Y-10) ----[2]
Avg price per unit is 20.
Therefore,
([1] + [2])/ (X+Y) = 20
On solving above equation we get ,
3X + 2Y = 90
Hence from answer options we have X = 20 , Y = 15.
Cost = Fixed cost + Cost of first 10 products + Cost of remaining products.
For X,
Cost = 100 + 20x10 + 5 (X-10) ----[1]
For Y,
Cost = 150 + 10x10 + 10 (Y-10) ----[2]
Avg price per unit is 20.
Therefore,
([1] + [2])/ (X+Y) = 20
On solving above equation we get ,
3X + 2Y = 90
Hence from answer options we have X = 20 , Y = 15.
Quote:
Video solution given here:
We know that at least 10 units were bought from each supplier.
Cost of first 10 units from X = 100 + 20*10 = 300
Cost of first 10 units from Y = 150 + 15*10 = 300
So on average cost of first 20 units was $30 per unit. Now additional units are bought at cheaper price of $5 per unit or $10 per unit. The average price of all these additional units would be between $5 and $10 say it is $n. But the overall average is $20 which is closer to the $30 price. Hence number of additional units bought must be less than 20.
Of the given options, there are only 2 possible options - 15 and 20 (additional units 15) or 15 and 22 (additional units 17). In all other cases, additional units will be more than 20 which is not acceptable. We will check for one of them. If that doesn't work, we know that the other one will.
Try additional units 15. Then the weights are 15 and 20 which means that
\(\frac{3}{4} = \frac{(30 - 20)}{(20 - n)}\)
\(x = $\frac{20}{3}\)
This is the average of $5 and $10.
\(\frac{w1}{w2} = \frac{(10 - 20/3)}{(20/3 - 5)} = 2:1\)
Hence 10 additional units were bought at $5 and 5 additional units were bought at $10. So 20 units were bought from X and 15 were bought from Y.
ANSWER: 20 from X and 15 from Y
Note that the solution looks long with multiple calculations but while solving it, you can do it directly on a single number line (using scale method). It happens much faster (shown in the video)
For scale method of weighted averages, check:
_________________
-
Start FREE with selected GMAT/EA Content upon registration at anaprep.com
YouTube Channel: karishma.anaprep
Start FREE with selected GMAT/EA Content upon registration at anaprep.com
YouTube Channel: karishma.anaprep
General Discussion
Oppenheimer1945
Joined: 16 Jul 2019
Last visit: 23 Aug 2026
Posts: 787
Location: India
Schools: INSEAD '26 (D) ISB '27 (D) IIMB '26 (A) IIMA '26 (A) HEC '26 (D) LBS '26 IESE '27 (D) Fuqua '27 (WL) Tepper '27 (WL)
GMAT Focus 1: 645 Q90 V76 DI80 
GPA: 7.81
Schools: INSEAD '26 (D) ISB '27 (D) IIMB '26 (A) IIMA '26 (A) HEC '26 (D) LBS '26 IESE '27 (D) Fuqua '27 (WL) Tepper '27 (WL)
GMAT Focus 1: 645 Q90 V76 DI80
Posts: 787
A: 100+200+5(a-10)=5a+250
B: 150+150+10(b-10)=10b+200
Avg=0.5(5a+10b+450)
equals
20(a+b)
20(a+b)=5a+10b+450
=>15a+10b=450
=>3a+2b=90
Options-10: 5,10,12,15,17,20
a=20, b=15
B: 150+150+10(b-10)=10b+200
Avg=0.5(5a+10b+450)
equals
20(a+b)
20(a+b)=5a+10b+450
=>15a+10b=450
=>3a+2b=90
Options-10: 5,10,12,15,17,20
a=20, b=15
Posts: 30
Cost X = 100 + 20x10 + 5 (X-10)
Cost Y = 150 + 10x10 + 10 (Y-10)
Average = (Cost X + Cost Y)/ (X+Y) = 20
450 + 5X + 10Y = 20X + 20Y
3X + 2Y = 90
X +2/3*Y = 30
=> Y must be divisible by 3 = 15, 27, 30
Y= 15; X = 20
Cost Y = 150 + 10x10 + 10 (Y-10)
Average = (Cost X + Cost Y)/ (X+Y) = 20
450 + 5X + 10Y = 20X + 20Y
3X + 2Y = 90
X +2/3*Y = 30
=> Y must be divisible by 3 = 15, 27, 30
Y= 15; X = 20
Posts: 7
There can be an alternate method which i used :
For supplier X : 100 (fixed) + 20 (10) + x = 100 + 200 + y = 300 + x
For Y : 150 (fixed) + 15 (10) + y = 150 + 150 + y = 300 + y
Now we know average unit price is 20 $ i.e, 300 + x + 300 + y / no. of items = 20
This also gives an estimation that total qty. combining x and y should be greater than 30.
I started to look for combination of 35 and just verified where i can get 20$ unit price.
Prepared additional table for additional prices (beyond 10 qty.) below
300 + (50) + 300 + (50) / 15 + 20 = 700/35 = 20
P.S : This method can be inefficient if table have more fields but considering the current question, using above it can be solved in lesser time.
GMAT-Club-Forum-17py5gko.png [ 3.73 KiB | Viewed 7026 times ]
For supplier X : 100 (fixed) + 20 (10) + x = 100 + 200 + y = 300 + x
For Y : 150 (fixed) + 15 (10) + y = 150 + 150 + y = 300 + y
Now we know average unit price is 20 $ i.e, 300 + x + 300 + y / no. of items = 20
This also gives an estimation that total qty. combining x and y should be greater than 30.
I started to look for combination of 35 and just verified where i can get 20$ unit price.
Prepared additional table for additional prices (beyond 10 qty.) below
300 + (50) + 300 + (50) / 15 + 20 = 700/35 = 20
P.S : This method can be inefficient if table have more fields but considering the current question, using above it can be solved in lesser time.
Attachment:
GMAT-Club-Forum-17py5gko.png [ 3.73 KiB | Viewed 7026 times ]
3x+2y=40 where x and y are the excess units of X and Y
x = (40-2y)/3
Is x is an integer, 40-2y should be a multiple of 3..
y=5, x=10 ; total 15, 20
y=8, x= 8 ; total 18 ,26
y=11, x=6.. you get the pattern.. y=5,8,11,14.. x=10,8,6,4,2...
x = (40-2y)/3
Is x is an integer, 40-2y should be a multiple of 3..
y=5, x=10 ; total 15, 20
y=8, x= 8 ; total 18 ,26
y=11, x=6.. you get the pattern.. y=5,8,11,14.. x=10,8,6,4,2...
Dear experts gmatophobia Bunuel KarishmaB
It is given, the combined average is 20. when we talk about "combine avg" then it means we are taking the avg of a gp in which elements are avg itself. But here, we are taking avg of total cost for X and Y as 20, instead avg cost per item of X and avg cost per item of Y as 20 ??
kindly clear my doubt.
It is given, the combined average is 20. when we talk about "combine avg" then it means we are taking the avg of a gp in which elements are avg itself. But here, we are taking avg of total cost for X and Y as 20, instead avg cost per item of X and avg cost per item of Y as 20 ??
kindly clear my doubt.
Can,Will
We are given "... the combined average cost for the units was $20 per unit."
We are given that the average of the cost per item is $20. The individual costs are $5, $10 and $30 per item. We have taken them in quantities such that the average per item comes out to be $20. Does that clear your doubt?
I have discussed the weighted args approach using a scale for this question here: https://youtu.be/waWVH6zPj-4
_________________
-
Start FREE with selected GMAT/EA Content upon registration at anaprep.com
YouTube Channel: karishma.anaprep
Start FREE with selected GMAT/EA Content upon registration at anaprep.com
YouTube Channel: karishma.anaprep
The highlighted should be 10x15
Garvesh
Posts: 28
In your solution, for eq 2, shouldn't it have been 10x15?
Garvesh
Hi ZeroSquare,
Good catch, you're reading the problem correctly.
You're looking at Garvesh's equation [2] for Supplier Y:
Cost = 150 + 10×10 + 10(Y-10)
The stem says Supplier Y charged $15 per unit for each of the first 10 units (the $10 rate is only for units beyond the first 10). So that middle term should indeed be 15 × 10 = 150, not 10 × 10. What's written there is a typo.
The correct setup for Y is:
- Fixed cost: 150
- First 10 units: 15 × 10 = 150
- Excess units: 10 × (Y - 10)
- Total: 150 + 150 + 10(Y - 10) = 200 + 10Y
Here's the reassuring part: even though the posted line shows 10×10, the final equation Garvesh landed on - 3X + 2Y = 90 - is the one you get from the correct $15 value. If you actually used 10×10, you'd get a total of 400 + 5X + 10Y, which leads to 3X + 2Y = 80, not 90. So the written term is just a slip; the real value $15 was used to reach the answer.
Let me confirm the full correct system:
- Supplier X: 100 + 20×10 + 5(X - 10) = 250 + 5X
- Supplier Y: 150 + 15×10 + 10(Y - 10) = 200 + 10Y
- Average = $20: 450 + 5X + 10Y = 20(X + Y) - therefore90 = 3X + 2Y
Plug in X = 20: 60 + 2Y = 90 - henceY = 15. Both are on the option list, so Supplier X = 20, Supplier Y = 15.
So trust your instinct - it's 15×10 for Y's first 10 units.
Answer: Column 1 = 20; Column 2 = 15
_________________
Good catch, you're reading the problem correctly.
You're looking at Garvesh's equation [2] for Supplier Y:
Cost = 150 + 10×10 + 10(Y-10)
The stem says Supplier Y charged $15 per unit for each of the first 10 units (the $10 rate is only for units beyond the first 10). So that middle term should indeed be 15 × 10 = 150, not 10 × 10. What's written there is a typo.
The correct setup for Y is:
- Fixed cost: 150
- First 10 units: 15 × 10 = 150
- Excess units: 10 × (Y - 10)
- Total: 150 + 150 + 10(Y - 10) = 200 + 10Y
Here's the reassuring part: even though the posted line shows 10×10, the final equation Garvesh landed on - 3X + 2Y = 90 - is the one you get from the correct $15 value. If you actually used 10×10, you'd get a total of 400 + 5X + 10Y, which leads to 3X + 2Y = 80, not 90. So the written term is just a slip; the real value $15 was used to reach the answer.
Let me confirm the full correct system:
- Supplier X: 100 + 20×10 + 5(X - 10) = 250 + 5X
- Supplier Y: 150 + 15×10 + 10(Y - 10) = 200 + 10Y
- Average = $20: 450 + 5X + 10Y = 20(X + Y) - therefore90 = 3X + 2Y
Plug in X = 20: 60 + 2Y = 90 - henceY = 15. Both are on the option list, so Supplier X = 20, Supplier Y = 15.
So trust your instinct - it's 15×10 for Y's first 10 units.
Answer: Column 1 = 20; Column 2 = 15
ZeroSquare
_________________
Free Trial: Get 25 AI-powered videos | 400 practice questions | 8 free webinars | 1 full + 3 sectional mocks
Record Success delivered in 2025-26: 100th percentile scores | 250-pt improvements | Success in less than 60 days
MBA admits: M7 admits | T20 admits | ISB admits | $100k Scholarships
Learn why e-GMAT has 2X more verified 705+ scores than other GMAT Club partners – Read our 2800+ reviews
Record Success delivered in 2025-26: 100th percentile scores | 250-pt improvements | Success in less than 60 days
MBA admits: M7 admits | T20 admits | ISB admits | $100k Scholarships
Learn why e-GMAT has 2X more verified 705+ scores than other GMAT Club partners – Read our 2800+ reviews
A=100+200+5(p−10)=5p+250
B = 150+150+10(q-10)=10q+200
Average=0.5(5p+10q+450)
0.5(5p+10q+450)=20(p+q)
3p+2q=90
Checking solutions; 20, 15
B = 150+150+10(q-10)=10q+200
Average=0.5(5p+10q+450)
0.5(5p+10q+450)=20(p+q)
3p+2q=90
Checking solutions; 20, 15
Moderators:
Announcements
Tuck at Dartmouth
AI at Dartmouth Tuck: How the School Is Preparing Leaders for the Age of Artificial Intelligence
Inside the courses, research, and hands-on learning defining wise, decisive leadership in an AI-driven world.
Read More
Inside the courses, research, and hands-on learning defining wise, decisive leadership in an AI-driven world.
Read More
Top 5 GMAT Debrief Videos
Success stories and strategies from high-scoring candidates.