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If a, b, c are integers, what is value of a+b+c?

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Source: — Data Sufficiency |

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by Jay@ManhattanReview » Mon Oct 30, 2017 1:39 am
M7MBA wrote:If a, b, c are integers, what is value of a+b+c?

(1) a^2+b^2+c^2=27.
(2) ab+ac+bc=11.

The OA is E.

I thought both statements together are sufficient. Why aren't they?
Though this formula is out of the scope of the GMAT, you may know it.

(a + b + c)^2 = a^2 + b^2 + c^2 + 2ab + 2bc + 2ca

Thus, (a + b + c)^2 = 27 + 2.11 = 49

=> a + b + c = ±7. No unique value. Insufficient

The correct answer: E

Hope this helps!

-Jay

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