NEW HERE? LEARN MORE
closeclose
Last visit was: 26 Apr 2024, 02:03 It is currently 26 Apr 2024, 02:03
Decision Tracker
My Rewards
New posts
New comers' posts

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

If the average (arithmetic mean) of x and y is 60 and the average (ari

SORT BY:
Date
Kudos
Tags:
Find Similar Topics 
Show Tags
Hide Tags
User avatar
tinman1412
Intern
Intern
Joined: 08 Sep 2006
Posts: 38
Own Kudos [?]: 225 [20]
Given Kudos: 0
Send PM
If the average (arithmetic mean) of x and y is 60 and the average (ari [#permalink] New post   23 Jul 2007, 19:33
7
Kudos
13
Bookmarks
00:00
A
B
C
D
E

Difficulty:

5% (low)

Question Stats:

91% (00:54) correct 9% (01:10) wrong based on 1344 sessions
Hide Show timer Statistics
If the average (arithmetic mean) of x and y is 60 and the average (arithmetic mean) of y and z is 80, what is the value of z-x?.

A. 70
B. 40
C. 20
D. 10
E. It cannot be determined from the information.
ShowHide Answer
Official Answer
B
Most Helpful Reply
User avatar
run4run
Manager
Manager
Joined: 02 Aug 2009
Posts: 84
Own Kudos [?]: 196 [6]
Given Kudos: 1
Send PM
Re: If the average (arithmetic mean) of x and y is 60 and the average (ari [#permalink] New post   01 Feb 2010, 17:55
3
Kudos
3
Bookmarks
(X + Y)/2=60 (Z + Y)/2=80


So Z + Y=160
X+Y = 120
Subtract the equations

and we get Z - X (the Y's cancel) = 40

so answer choice B.

Hope that helps
General Discussion
User avatar
ywilfred
SVP
SVP
Joined: 07 Jul 2004
Posts: 2004
Own Kudos [?]: 1899 [1]
Given Kudos: 0
Location: Singapore
Send PM
Re: If the average (arithmetic mean) of x and y is 60 and the average (ari [#permalink] New post   23 Jul 2007, 19:37
1
Kudos
(x+y)/2 = 60
x+y = 120 ---[1]

(y+z)/2 = 80
y+z = 160 ---[2]

[2]-[1]
z-x = 40
User avatar
qtip
Intern
Intern
Joined: 08 Sep 2006
Posts: 26
Own Kudos [?]: [0]
Given Kudos: 0
Send PM
Re: If the average (arithmetic mean) of x and y is 60 and the average (ari [#permalink] New post   24 Jul 2007, 07:48
tinman1412 wrote:
If the average (arithmetic mean) of x and y is 60 and the average (arithmetic mean) of y and z is 80, what is the value of z-x?.

a)70
b)40
c)20
d)10
e)It cannot be determined from the information.

This question is from the OG 10, but I do not understand their explanation. Hopefully someone can give me their approach.

Thanks,


I did this problem a couple of ways but it is essential the same as other posters.

(x+y)/2 = 60 (from avg formula)
(y+z)/2 = 80 (from avg formula)

set both equal to each other but we need to subtract 20 from 2nd equation to ensure they are equal (60):

(x+y)/2 = (y+z)/2 - 20 ->
x+y = y+z - 40 ->
z - x = 40
User avatar
B
mau5
Verbal Forum Moderator
Joined: 10 Oct 2012
Posts: 485
Own Kudos [?]: 3093 [2]
Given Kudos: 141
Send PM
Re: If the average (arithmetic mean) of x and y is 60 and the average (ari [#permalink] New post   16 Jun 2013, 01:13
2
Kudos
tinman1412 wrote:
If the average (arithmetic mean) of x and y is 60 and the average (arithmetic mean) of y and z is 80, what is the value of z-x?.

A. 70
B. 40
C. 20
D. 10
E. It cannot be determined from the information.


10 second approach :

Mean of x and y is 60. We can assume both x = y = 60. Again, mean of y and z is 80; We can keep the value of y = 60 and assume the value of z = 100. Thus, z-x = 100-60 = 40.

B.
User avatar
stormbind
Intern
Intern
Joined: 08 Jan 2013
Posts: 28
Own Kudos [?]: 105 [0]
Given Kudos: 5
Send PM
Re: If the average (arithmetic mean) of x and y is 60 and the average (ari [#permalink] New post   16 Jun 2013, 02:04
That's brilliant Mau5. Do you know of a guide with general speed tips?
User avatar
B
mau5
Verbal Forum Moderator
Joined: 10 Oct 2012
Posts: 485
Own Kudos [?]: 3093 [0]
Given Kudos: 141
Send PM
Re: If the average (arithmetic mean) of x and y is 60 and the average (ari [#permalink] New post   16 Jun 2013, 02:26
stormbind wrote:
That's brilliant Mau5. Do you know of a guide with general speed tips?


As for general speed tips, as it is with everyone on gmatclub, I have learnt a lot by just observing Bunuel's solutions! In this case particularly, what I did is just one of the many ways of interpreting averages,i.e. if average of 2 things is X, then each of them can be assumed to be X.
User avatar
L
EMPOWERgmatRichC
GMAT Club Legend
GMAT Club Legend
Joined: 19 Dec 2014
Status:GMAT Assassin/Co-Founder
Affiliations: EMPOWERgmat
Posts: 21846
Own Kudos [?]: 11668 [1]
Given Kudos: 450
Location: United States (CA)
GMAT 1: 800 Q51 V49
GRE 1: Q170 V170
Send PM
Re: If the average (arithmetic mean) of x and y is 60 and the average (ari [#permalink] New post   19 Sep 2015, 17:17
1
Kudos
Expert Reply
Hi All,

While most Test Takers would use an algebra approach to answer this question (which is fine), this prompt can also be solved by TESTing VALUES....

We're told that (X+Y)/2 = 60 and (Y+Z)/2 = 80. With a little algebra, we can rewrite these equations as...

X+Y = 120
Y+Z = 160

We're asked for the value of Z-X....

IF....
X = 60
Y = 60
Z = 100

So, Z-X = 100-60 = 40

No matter what values you TEST for X, Y and Z, the answer will always be the same (go ahead and try it and you'll see!).

Final Answer:
Show Spoiler
B


GMAT assassins aren't born, they're made,
Rich
User avatar
B
LogicGuru1
Senior Manager
Senior Manager
Joined: 04 Jun 2016
Posts: 484
Own Kudos [?]: 2335 [0]
Given Kudos: 36
GMAT 1: 750 Q49 V43
Send PM
Re: If the average (arithmetic mean) of x and y is 60 and the average (ari [#permalink] New post   23 Jul 2016, 07:43
tinman1412 wrote:
If the average (arithmetic mean) of x and y is 60 and the average (arithmetic mean) of y and z is 80, what is the value of z-x?.

A. 70
B. 40
C. 20
D. 10
E. It cannot be determined from the information.


\(\frac{X+Y}{2}=60 ; X+Y=120\)

\(\frac{Y+Z}{2}=80 ; Y+Z=160\)

\((Y+Z)-(X+Y)= 160-120\)

\(Y+Z-X-Y=40\) (+Y AND -Y CANCELS EACH OTHER)

\(Z-X=40\)

ANSWER IS B
User avatar
L
ScottTargetTestPrep
Target Test Prep Representative
Joined: 14 Oct 2015
Status:Founder & CEO
Affiliations: Target Test Prep
Posts: 18761
Own Kudos [?]: 22055 [1]
Given Kudos: 283
Location: United States (CA)
Send PM
Re: If the average (arithmetic mean) of x and y is 60 and the average (ari [#permalink] New post   16 Oct 2016, 18:20
1
Kudos
Expert Reply
tinman1412 wrote:
If the average (arithmetic mean) of x and y is 60 and the average (arithmetic mean) of y and z is 80, what is the value of z-x?.

A. 70
B. 40
C. 20
D. 10
E. It cannot be determined from the information.


We are given that the average (arithmetic mean) of x and y is 60 and the average (arithmetic mean) of y and z is 80. We can create the following equations:

Equation 1:

(x + y)/2 = 60

x + y = 120

y = 120 - x

Equation 2:

(y + z)/2 = 80

y + z = 160

y = 160 - z

Since y = 120 - x and y = 160 - z, we can equate the two expressions.

120 - x = 160 - z

z - x = 40

Answer: B
User avatar
L
ScottTargetTestPrep
Target Test Prep Representative
Joined: 14 Oct 2015
Status:Founder & CEO
Affiliations: Target Test Prep
Posts: 18761
Own Kudos [?]: 22055 [0]
Given Kudos: 283
Location: United States (CA)
Send PM
Re: If the average (arithmetic mean) of x and y is 60 and the average (ari [#permalink] New post   19 Dec 2016, 10:56
Expert Reply
roceeet wrote:
If the average (arithmetic mean) of x and y is 60 and the average (arithmetic mean) of y and z is 80, what is the value of \(z - x\)?

(a) 70
(b) 40
(c) 20
(d) 10
(e) It cannot be determined from the information given.


We are given that the average of x and y is 60. Thus:

(x + y)/2 = 60

x + y = 120

x = 120 - y

We are also given that the average of y and z is 80. Thus:

(y + z)/2 = 80

z = 160 - y

Since x = 120 - y and z = 160 - y:

z - x = 160 - y - (120 - y) = 160 - 120 = 40

Answer: B
User avatar
voccubd
Intern
Intern
Joined: 08 Oct 2016
Posts: 10
Own Kudos [?]: 101 [0]
Given Kudos: 11
Send PM
Re: If the average (arithmetic mean) of x and y is 60 and the average (ari [#permalink] New post   29 Dec 2016, 09:31
EMPOWERgmatRichC wrote:
Hi All,

While most Test Takers would use an algebra approach to answer this question (which is fine), this prompt can also be solved by TESTing VALUES....

We're told that (X+Y)/2 = 60 and (Y+Z)/2 = 80. With a little algebra, we can rewrite these equations as...

X+Y = 120
Y+Z = 160

We're asked for the value of Z-X....

IF....
X = 60
Y = 60
Z = 100

So, Z-X = 100-60 = 40

No matter what values you TEST for X, Y and Z, the answer will always be the same (go ahead and try it and you'll see!).

Final Answer:
Show Spoiler
B


GMAT assassins aren't born, they're made,
Rich

What if I need to find the value of z-y. How to approach that?
User avatar
L
EMPOWERgmatRichC
GMAT Club Legend
GMAT Club Legend
Joined: 19 Dec 2014
Status:GMAT Assassin/Co-Founder
Affiliations: EMPOWERgmat
Posts: 21846
Own Kudos [?]: 11668 [0]
Given Kudos: 450
Location: United States (CA)
GMAT 1: 800 Q51 V49
GRE 1: Q170 V170
Send PM
Re: If the average (arithmetic mean) of x and y is 60 and the average (ari [#permalink] New post   29 Dec 2016, 11:03
Expert Reply
Hi voccubd,

Unfortunately, the 'design' of this question does NOT given you the necessary information to answer THAT question. You have to remember that NOTHING about a GMAT question is ever 'random' - the information that you're given is specific, the wording is specific and the numbers involved were specifically chosen by whoever wrote the prompt... to help you answer the specific question that is asked. The prompt would have to be rewritten for you to properly answer the question that you're asking about.

GMAT assassins aren't born, they're made,
Rich
User avatar
L
Abhishek009
Board of Directors
Joined: 11 Jun 2011
Status:QA & VA Forum Moderator
Posts: 6072
Own Kudos [?]: 4690 [0]
Given Kudos: 463
Location: India
GPA: 3.5
WE:Business Development (Commercial Banking)
Send PM
GMAT ToolKit User
Re: If the average (arithmetic mean) of x and y is 60 and the average (ari [#permalink] New post   29 Dec 2016, 11:13
roceeet wrote:
If the average (arithmetic mean) of x and y is 60 and the average (arithmetic mean) of y and z is 80, what is the value of \(z - x\)?

(a) 70
(b) 40
(c) 20
(d) 10
(e) It cannot be determined from the information given.


x + y = 120
y + z = 160

So, z = 160 - y and y = 120 - x

Or, z = 160 - ( 120 - x )

Or, z = 160 - 120 + x

Or, z - x = 40

Hence, correct answer will be (B) 40
User avatar
D
Snehaaaaa
Manager
Manager
Joined: 09 Mar 2021
Posts: 144
Own Kudos [?]: 286 [0]
Given Kudos: 161
Location: India
Schools: Booth '24 ISB '23 Ross '24 Sloan '24 Wharton '24 Haas '25 Kellogg '24 Anderson '25
GMAT 1: 640 Q44 V34
GPA: 3.68
Send PM
Re: If the average (arithmetic mean) of x and y is 60 and the average (ari [#permalink] New post   18 Jan 2022, 21:58
tinman1412 wrote:
If the average (arithmetic mean) of x and y is 60 and the average (arithmetic mean) of y and z is 80, what is the value of z-x?.

A. 70
B. 40
C. 20
D. 10
E. It cannot be determined from the information.


Explanation-

(x+y)/2 = 60
(y+z)/2 = 80
Value of z-x = ?

Solving,
x+y =120 ==> y= 120-x

y+z =160
Substituting y= 120-x,
120-x+z =160
z-x =40
User avatar
B
ArnauG
Senior Manager
Senior Manager
Joined: 23 Dec 2022
Posts: 318
Own Kudos [?]: 35 [0]
Given Kudos: 199
Send PM
Re: If the average (arithmetic mean) of x and y is 60 and the average (ari [#permalink] New post   29 May 2023, 00:23
To find the value of z - x, we need to determine the values of both z and x.

Given that the average of x and y is 60, we can write the equation:
(x + y) / 2 = 60

Similarly, the average of y and z is 80:
(y + z) / 2 = 80

We can rearrange the first equation to solve for y:
x + y = 120
y = 120 - x

Substituting this value of y into the second equation, we get:
(120 - x + z) / 2 = 80
120 - x + z = 160
z - x = 40

Therefore, the value of z - x is 40.
GMAT Club Bot
gmatclubot
Re: If the average (arithmetic mean) of x and y is 60 and the average (ari [#permalink]
29 May 2023, 00:23
Moderators:
Bunuel
Math Expert
92921 posts
yashikaaggarwal
Senior Moderator - Masters Forum
3137 posts

Powered by phpBB © phpBB Group | Emoji artwork provided by EmojiOne
Main navigation
GMAT Resources
Partners
MBA Resources
www.gmac.com|www.mba.com | | GMAT Club Rules | Terms and Conditions