Data Sufficiency

Hello All. Please be gentle as this is my first post in asking a problem question.

This is probably a very simple DS question from Princeton's Cracking the GMAT book, but I'm just not seeing the solution given by Princeton.

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

1) x = 2
2) a = 5

Actual answer is suppose to be (B) but I don't see how one could obtain the value of z, and thus the ultimate answer to "what is x+y+z?" I want to answer (E).

Please expound on why the correct answer should be B.

Thanks!

Hi Alpha

Its a typo on Princeton's part. I saw two questions in OG that had a typo. So relax...no way in hell can the solution be known if Z is not given in the question.

Ankush2008 wrote:Hi Alpha

Its a typo on Princeton's part. I saw two questions in OG that had a typo. So relax...no way in hell can the solution be known if Z is not given in the question.

Hi Ankush2008, well here is the official explanation from Princeton why the answer should be (B) but I don't see it. Take a look:

Statement (1) gives us a value of x, but we need x + y + d. Statement (1) is not sufficient. We're down to BCE. Statement (2) might not have seemed much more helpful, BUT using the distributive property, we can rewrite the original equation to read a (x+y+z) = 15. If a is 5, then x + y + z must equal 3. The correct answer is choice B.

This is an exact quote, including what I believe to be a typo highlighted in red above. I don't know why they suddenly introduced the variable "d" in their solution, but I believe they're actually referring to the variable "z" above. Nevertheless, does their solution make sense?

I'm having a very difficult time with DS problem sets in general because I've never had to solve DS problems before--like most people--and it's just very strange. I'm always trying to solve the whole problem.

Anyway, given their solution above, do you still think it's a typo? Or is their answer B correct?

Thanks.

Based on the answer, it looks like the question should have been written as "ax+ay+az=15" because in the official answer, they write a(x+y+z)=15 and this is only possible if the question was written as shown above.

I don't know what they did in statement (1) in their official answer. Looks funky to me. I think its safe to assume that the question was just written wrong.

newera wrote:Based on the answer, it looks like the question should have been written as "ax+ay+az=15" because in the official answer, they write a(x+y+z)=15 and this is only possible if the question was written as shown above.

I don't know what they did in statement (1) in their official answer. Looks funky to me. I think its safe to assume that the question was just written wrong.

Thanks for your comments.

These books indeed have quite a few typos/errors. I found a couple of other wrong answers and typos. Bad bad bad! It makes an already confusing situation even more confusing.

Either the prob mentioned is wrong.

but i couldnt derive how you come to this conclusion

a(x+y)=15
a(x+y+z) =15....are you assuming z = 0..

...
Gaurav

I think it should be E, or the problem is asking x + y

Exentrick1, how does the z magically gets introduced after you factor a ?