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

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!

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.

yes it is when you format it like that!

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

is how I read the equation.

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.

As I said I misread the question because it wasn't clearly formatted as 3 seperate equations.

No need to call me sad

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

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?

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.

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.

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.

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