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The question

Ok, so this question is from seriously hard IQ test that has been doing the rounds on facebook, ok, 17 questions are easy 3 are hellishly hard, The answer to this one is 17, I do not know why, I found out by trial and error just to test, but It's killing me, anyone know why?

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up vote 10 down vote accepted

Note that $1+3+4+9=17$ and $1+7+1+0=9$.

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Nice catch. $\phantom{i}$ – Newb Feb 5 '14 at 2:52
you sir, are brilliant – user126285 Feb 5 '14 at 3:00

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