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Simple Question

Expert replies
by NYC_Kid » Sun Jun 21, 2009 8:22 am
A Data Sufficiency problem from Princeton Review:

If ax + ay=15, what is x+y+z?

(1) x=2

(2) a=5

Answer down below:

[spoiler]Statement (1) gives us a value for x, but we need x+y+d. Statemnt (1) is not sufficient. We're down to Statement 2, 3 and 4. Statement (2) might not have seemed much more helpful, but using the distributive property, we can rewrite the orginal equation to read a(x+y+z)=15. If a is 5, then x+y+z must equal 3. The correct answer is Statement 2.[/spoiler]

--------

-The bolded in red is a typo right? Where did they get d?

-I don't see what they did in the 2nd bolded part in purple? The equation is ax+ay=15, which would factor to a(x+y)=15 and if A is 5, then x+y would equal to 3, but we still wouldn't know what Z would be.

Thus I picked choice E, "statements (1) and (2) together are not sufficient.
Last edited by NYC_Kid on Sun Jun 21, 2009 8:44 am, edited 1 time in total.
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Source: — Data Sufficiency |

Re: Simple Question

by iamcste » Sun Jun 21, 2009 8:34 am
NYC_Kid wrote:A Data Sufficiency problem from Princeton Review:

If ax + ay=15, what is x+y+z?

(1) x=5

(2) a=5:
we can rewrite the orginal equation to read a(x+y+z)=15
If a is 5, then x+y+z must equal 3.
Did you miss "az" in the original equation
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by NYC_Kid » Sun Jun 21, 2009 8:43 am
No, actually there is one typo. X=2, not X=5.

Heres a picture I took of the picture with my camera:

https://i43.tinypic.com/35c225z.jpg

Here's the answer:

https://i40.tinypic.com/124yeft.jpg

I'm confused.
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by mikeCoolBoy » Sun Jun 21, 2009 9:19 am
iamcste is right.

according to the explanation the question should provide the following information

ax + ay + az = 15

then you can apply a(x+y+z) = 15 and since a = 5
x + y + z = 3
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by Ian Stewart » Sun Jun 21, 2009 11:35 am
There seem to be several errors in that question/explanation. First, they say 'it is not uncommon to see a data sufficiency problem like this'. You would never see a DS question like this one; the answer is obviously E since you have no information about z. The solution then says we need "x + y + d", but the question asks about x + y + z. Finally, they introduce a 'z' out of nowhere in the solution when they produce the expression "a(x + y + z)". As Mike points out, they surely intended to write "ax + ay + az" in the question.
For online GMAT math tutoring, or to buy my higher-level Quant books and problem sets, contact me at ianstewartgmat at gmail.com

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by Domnu » Thu Jun 25, 2009 3:48 pm
If so, the answer would be B.

We can't do anything with 1).

With 2), 5 * (x + y + z) = 15, so x + y + z = 3.
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