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

Question

Question taken from Cracking the GMAT 2009 edition - Princeton Review If ax + ay = 15, what is x + y + z ? (1) x = 2 (2) a = 5 My personal answer is E (statement 1 and 2 together is not sufficient) but refer to the answer key, it should be B (statement 2 alone is sufficient but statement 1 is not sufficient) Kinda confused

if we used statement 2 to answer the question, we still need to know what is the value of z, right? advice please (FYI, I did proofread for the question and answer several times)

scthakur · Answer

Please check whether the question asks for (x+y+z) or (x+y+2).

juliuscarsienly · Answer

it is z (like as Zebra)

Do you need me to scan it send it personally to you?

scthakur · Answer

Then, it must be a type in their book. Have they given OE?

juliuscarsienly · Answer

Sorry, what is OE?

They give an explanation as follow:

statement (1) gives us a value for x, but we need  x+y+d . (which I think should be  x+y+z )
Statement (1) is not sufficient. We're down to BCE. Statement (1) might not have seemed mocuh 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.

In my humble opinion, with explanation as above and correct answer is B, then the question should be:

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

advice please,

rgd, Julius

GmatEnemy · Answer

Its definitely a mistake.. Z cant be identified unless anything related to it is given

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

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