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

Redeem

Arithmetic mean(4)

This topic has expert replies
Post new topic Post Reply
Previous Topic Next Topic
Senior | Next Rank: 100 Posts
Posts: 32
Joined: Fri Feb 19, 2010 12:36 pm
Location: Pennsylvania
Thanked: 1 times

Arithmetic mean(4)

by tsmith93 » Wed Mar 03, 2010 6:42 pm
x +y = 10 y + z = 15 x + z = 17

What is the average (arithmetic mean) of x, y, and z?

(A) 7
(B) 14
(C) 15
(D) 21
(E) It cannot be determined from the information given.
Top
Source: — Problem Solving |
Master | Next Rank: 500 Posts
Posts: 392
Joined: Thu Jan 15, 2009 12:52 pm
Location: New Jersey
Thanked: 76 times

by truplayer256 » Wed Mar 03, 2010 8:20 pm
Add all three of those equations to obtain:

2x+2y+2z=42

x+y+z=21

We want the arithmetic mean of x+y+z or x+y+z/3.

Answer=21/3=7
Top
Senior | Next Rank: 100 Posts
Posts: 45
Joined: Tue Mar 02, 2010 4:27 am
Thanked: 2 times

by yeahdisk » Fri Mar 05, 2010 3:06 am
Hi - how did you add the equations together to get your first equation?

I ended up in a great big loop of algebra and got an answer of -24!
Top
User avatar
Legendary Member
Posts: 1132
Joined: Mon Jul 20, 2009 3:38 am
Location: India
Thanked: 64 times
Followed by:6 members
GMAT Score:760

by harsh.champ » Fri Mar 05, 2010 3:11 am
yeahdisk wrote:Hi - how did you add the equations together to get your first equation?

I ended up in a great big loop of algebra and got an answer of -24!
Its pretty simple:-
x +y = 10
y + z = 15
x + z = 17

Adding LHS and RHS ,we get
2(x + y + z) = 42 [10 + 15 + 17 =42]
So, we have x+y+z = 21
or (x+y+z)/3 = 21/3 =7 which is the answer.

Hope the explanation helps.
It takes time and effort to explain, so if my comment helped you please press Thanks button :)



Just because something is hard doesn't mean you shouldn't try,it means you should just try harder.

"Keep Walking" - Johnny Walker :P
Top
Senior | Next Rank: 100 Posts
Posts: 45
Joined: Tue Mar 02, 2010 4:27 am
Thanked: 2 times

by yeahdisk » Fri Mar 05, 2010 3:16 am
yes it is when you format it like that!

(x +y) = (10y + z) = (15x + z) = 17

is how I read the equation.
Top
User avatar
GMAT Instructor
Posts: 3650
Joined: Wed Jan 21, 2009 4:27 am
Location: India
Thanked: 267 times
Followed by:80 members
GMAT Score:760

by sanju09 » Fri Mar 05, 2010 3:16 am
yeahdisk wrote:Hi - how did you add the equations together to get your first equation?

I ended up in a great big loop of algebra and got an answer of -24!
So sad, IDK which algebraic flight you boarded on that led you to land on -24; it's in fact an age old simultaneous equation problem which has this only way of cracking as given by truplayer256.
The mind is everything. What you think you become. -Lord Buddha



Sanjeev K Saxena
Quantitative Instructor
The Princeton Review - Manya Abroad
Lucknow-226001

www.manyagroup.com
Top
Senior | Next Rank: 100 Posts
Posts: 45
Joined: Tue Mar 02, 2010 4:27 am
Thanked: 2 times

by yeahdisk » Fri Mar 05, 2010 3:22 am
As I said I misread the question because it wasn't clearly formatted as 3 seperate equations.

No need to call me sad
Top
User avatar
GMAT Instructor
Posts: 3650
Joined: Wed Jan 21, 2009 4:27 am
Location: India
Thanked: 267 times
Followed by:80 members
GMAT Score:760

by sanju09 » Fri Mar 05, 2010 3:22 am
yeahdisk wrote:yes it is when you format it like that!

(x +y) = (10y + z) = (15x + z) = 17

is how I read the equation.
Oh, now I see

Members are therefore requested to present their work in a well turned-out manner, you are now scot-free yeahdisk
The mind is everything. What you think you become. -Lord Buddha



Sanjeev K Saxena
Quantitative Instructor
The Princeton Review - Manya Abroad
Lucknow-226001

www.manyagroup.com
Top
Senior | Next Rank: 100 Posts
Posts: 84
Joined: Sat Oct 03, 2009 1:13 pm
Thanked: 11 times

by djkvakin » Fri Mar 05, 2010 11:42 am
I don't see how else would you read the question! x+y=10y+z=5x+z=17, all of the equations equal to 17.
I get x+y=17
10y+z=17
15x+z=17

If you add them all up, you get 16x+2z+11y=51

I need help understanding how you got x+y=10, etc.

What is the source if this question?
Top
User avatar
Legendary Member
Posts: 1132
Joined: Mon Jul 20, 2009 3:38 am
Location: India
Thanked: 64 times
Followed by:6 members
GMAT Score:760

by harsh.champ » Fri Mar 05, 2010 10:46 pm
tsmith93 wrote:x +y = 10 y + z = 15 x + z = 17

What is the average (arithmetic mean) of x, y, and z?

(A) 7
(B) 14
(C) 15
(D) 21
(E) It cannot be determined from the information given.
Guys read the question as shown above.

Also,just quote the original question :-You will see that the spacing between (10 and y) , (15 and x) is sufficient.
Only when the question is posted the spacing gets automatically reduced.


Maybe David can help know the problem over here.
It takes time and effort to explain, so if my comment helped you please press Thanks button :)



Just because something is hard doesn't mean you shouldn't try,it means you should just try harder.

"Keep Walking" - Johnny Walker :P
Top
User avatar
GMAT Instructor
Posts: 3650
Joined: Wed Jan 21, 2009 4:27 am
Location: India
Thanked: 267 times
Followed by:80 members
GMAT Score:760

by sanju09 » Sat Mar 06, 2010 1:11 am
harsh.champ wrote:
tsmith93 wrote:x +y = 10 y + z = 15 x + z = 17

What is the average (arithmetic mean) of x, y, and z?

(A) 7
(B) 14
(C) 15
(D) 21
(E) It cannot be determined from the information given.
Guys read the question as shown above.

Also,just quote the original question :-You will see that the spacing between (10 and y) , (15 and x) is sufficient.
Only when the question is posted the spacing gets automatically reduced.


Maybe David can help know the problem over here.
It's a doubtlessly doubtful case of multiple interpretations, although the spacing IS there, but that again is not as sufficient as that should have been to avoid multiple interpretations. A comma is the best deal for showing separation if we want to be economic with the number of lines used to write any text. We can't accuse a member for illicit staging of terms in their early 50 posts when they are more curious to learn than to exhibit their aptness. Since we cannot edit their work, so all we can do is to request them to edit their work so that ambiguity must not prevail. Even David won't do much more than that as he would also submit that the "Tab" button on our keyboard is not for here.
The mind is everything. What you think you become. -Lord Buddha



Sanjeev K Saxena
Quantitative Instructor
The Princeton Review - Manya Abroad
Lucknow-226001

www.manyagroup.com
Top
User avatar
GMAT Instructor
Posts: 3650
Joined: Wed Jan 21, 2009 4:27 am
Location: India
Thanked: 267 times
Followed by:80 members
GMAT Score:760

by sanju09 » Sat Mar 06, 2010 1:37 am
tsmith93 wrote:x +y = 10 y + z = 15 x + z = 17

What is the average (arithmetic mean) of x, y, and z?

(A) 7
(B) 14
(C) 15
(D) 21
(E) It cannot be determined from the information given.
A GMAT PS question scarcely embraces a choice that reads an info incompetency, for such questions always have a section in GMAT quantitative, which is well-liked as DS.
The mind is everything. What you think you become. -Lord Buddha



Sanjeev K Saxena
Quantitative Instructor
The Princeton Review - Manya Abroad
Lucknow-226001

www.manyagroup.com
Top
User avatar
GMAT Instructor
Posts: 3650
Joined: Wed Jan 21, 2009 4:27 am
Location: India
Thanked: 267 times
Followed by:80 members
GMAT Score:760

by sanju09 » Sat Mar 06, 2010 2:02 am
djkvakin wrote:I don't see how else would you read the question! x+y=10y+z=5x+z=17, all of the equations equal to 17.
I get x+y=17
10y+z=17
15x+z=17

If you add them all up, you get 16x+2z+11y=51

I need help understanding how you got x+y=10, etc.

What is the source if this question?
You made it even impenetrable, if it was so, then you were correct. But if you cannot understand harsh.champ's chromatography, then read the equations in the following manner and request tsmith93 to edit their work like that to avoid any confusion.

x + y = 10

y + z = 15

x + z = 17
The mind is everything. What you think you become. -Lord Buddha



Sanjeev K Saxena
Quantitative Instructor
The Princeton Review - Manya Abroad
Lucknow-226001

www.manyagroup.com
Top
Post new topic Post Reply
• Page 1 of 1