Last visit was: 12 Dec 2024, 10:33 It is currently 12 Dec 2024, 10:33
Home
GMAT
Messages
Tests
Schools
Reviews
Social
Chat
My Profile
Close
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
Close
Request Expert Reply
Confirm Cancel
Back to Forum
Create Topic
User avatar
AndreG
User avatar
Joined: 22 Jun 2010
Last visit: 09 Dec 2010
Posts: 29
Own Kudos:
271
 []
Given Kudos: 10
Posts: 29
Kudos: 271
 []
Is 20 the average (arithmetic mean) of u, v, w, and 20? 15 Jul 2010, 13:45
Kudos
Add Kudos
1
Bookmarks
Bookmark this Post
00:00
Start Timer
Pause Timer
Resume Timer
Show Answer
Hide
Show
History
A
Be sure to select an answer first to save it in the Error Log before revealing the correct answer (OA)!

Difficulty:

25% (medium)

Question Stats:

80% (01:54) correct 20% (01:44) wrong based on 99 sessions

History

Date
Time
Result
Not Attempted Yet
Is 20 the average (arithmetic mean) of u, v, w, and 20?

(1) u + v + w = 60

(2) u - v + w = 20, u + v - w =16

Show Spoiler
OA was A...

I believe it should be D - since adding the two equations provided in ST2 cancels out v + w, so we can solve for u, leaving us with 2 equations with 2 unknowns...
ShowHide Answer
Official Answer
A
User avatar
Bunuel
User avatar
Math Expert
Joined: 02 Sep 2009
Last visit: 12 Dec 2024
Posts: 97,847
Own Kudos:
685,343
 []
Given Kudos: 88,255
Products:
GMAT Club Tests Forum Quiz
Expert reply
Active GMAT Club Expert! Tag them with @ followed by their username for a faster response.
Posts: 97,847
Kudos: 685,343
 []
Is 20 the average (arithmetic mean) of u, v, w, and 20? 15 Jul 2010, 14:12
1
Kudos
Add Kudos
Bookmarks
Bookmark this Post
AndreG
Hi,
came across this just now and i believe the OA is wrong, please tell me what you think:

Is 20 the average (arithmetic mean) of u, v, w, and 20?

(1) u + v + w = 60

(2) u - v + w = 20, u + v - w =16

Show Spoiler
OA was A...

I believe it should be D - since adding the two equations provided in ST2 cancels out v + w, so we can solve for u, leaving us with 2 equations with 2 unknowns...

Have you tried to solve these 2 equations?

When you add \(u-v+w=20\) and \(u+v-w=16\) you'll get \(u=18\) and if you substitute the value of \(u\) in these two equations you'll get: for 1. \(18-v+w=20\) --> \(w-v=2\) and for 2. \(18+v-w=16\) --> \(w-v=2\), so two identical equations, thus you won't be able to solve for \(w\), \(v\) or for \(w+v\).

Statement to be sufficient you need \(n\) distinct linear equations for \(n\) variables.
User avatar
onedayill
User avatar
Joined: 25 Feb 2010
Last visit: 08 Mar 2017
Posts: 208
Own Kudos:
326
Given Kudos: 10
Posts: 208
Kudos: 326
Is 20 the average (arithmetic mean) of u, v, w, and 20? 19 Jul 2010, 09:10
Kudos
Add Kudos
Bookmarks
Bookmark this Post
you can;t solve from B.
u'll get the same equation.
User avatar
dauntingmcgee
User avatar
Joined: 16 Jul 2010
Last visit: 17 Aug 2010
Posts: 15
Own Kudos:
35
Given Kudos: 9
Posts: 15
Kudos: 35
Is 20 the average (arithmetic mean) of u, v, w, and 20? 20 Jul 2010, 12:53
Kudos
Add Kudos
Bookmarks
Bookmark this Post
AndreG

Show Spoiler
OA was A...

I believe it should be D - since adding the two equations provided in ST2 cancels out v + w, so we can solve for u, leaving us with 2 equations with 2 unknowns...

Using the information in 1) it is possible to solve for v and w in 2). However, in order for D to be correct, we would need to be able to solve for v and w using only the information in 2). Since 1) is sufficient and 2) is insufficient alone, the answer is A.
User avatar
whiplash2411
User avatar
Joined: 09 Jun 2010
Last visit: 02 Mar 2015
Posts: 1,762
Own Kudos:
3,519
Given Kudos: 210
Status:Three Down.
Concentration: General Management, Nonprofit
Schools: HBS '17 (M) Stanford '17 (A)
Schools: HBS '17 (M) Stanford '17 (A)
Posts: 1,762
Kudos: 3,519
Is 20 the average (arithmetic mean) of u, v, w, and 20? 20 Jul 2010, 13:14
Kudos
Add Kudos
Bookmarks
Bookmark this Post
I think as people have pointed out already, you need to make sure you actually know that the equation is solvable. Don't just think that since it simplifies to two equations with two variables you'll be able to solve it. It needs to be two distinct equations.
User avatar
saxenashobhit
User avatar
Joined: 20 Jul 2010
Last visit: 14 Nov 2013
Posts: 136
Own Kudos:
250
Given Kudos: 9
Products:
My Reviews
Posts: 136
Kudos: 250
Is 20 the average (arithmetic mean) of u, v, w, and 20? 21 Jul 2010, 13:55
Kudos
Add Kudos
Bookmarks
Bookmark this Post
We have to answer Is \(\frac{U+V+W+20}{4}\)=20? Or U+V+W+20 is 80

Option 1 gives sum total of all.
Option 2 alone doesn't

So answer is A
User avatar
bumpbot
User avatar
Non-Human User
Joined: 09 Sep 2013
Last visit: 04 Jan 2021
Posts: 35,797
Own Kudos:
929
Posts: 35,797
Kudos: 929
Is 20 the average (arithmetic mean) of u, v, w, and 20? 11 Aug 2017, 03:45
Kudos
Add Kudos
Bookmarks
Bookmark this Post
Hello from the GMAT Club BumpBot!

Thanks to another GMAT Club member, I have just discovered this valuable topic, yet it had no discussion for over a year. I am now bumping it up - doing my job. I think you may find it valuable (esp those replies with Kudos).

Want to see all other topics I dig out? Follow me (click follow button on profile). You will receive a summary of all topics I bump in your profile area as well as via email.
Moderator:
Bunuel
Math Expert
97847 posts