I have this puzzle that none of my colleagues (including me) can figure out and I can't sleep because of it :). Can someone please help: enter image description here

Thank you.

  • $\begingroup$ What does the hollow ellipse correspond to? $\endgroup$ Mar 11, 2016 at 11:09
  • 3
    $\begingroup$ "I can't sleep because of tit"... lol can't help you. $\endgroup$
    – Daedric
    Mar 11, 2016 at 11:16

1 Answer 1


My guess would be

the missing number is $3$


If we denote the four numbers by $a,b,c,d$, in clockwise order, starting with the lower left position (so that in the left picture $a=2$, $b=8$, $c=14$ and $d=9$), then these number satisfy the relation

$d*a-(b/a) = c~~~~$ Indeed, $9*2-(8/2)=14$ in the left picture.

In the right picture, the unknown $x=?$ then should satisfy $x*3-(15/3)=4$, which yields the answer $x=3$.

  • $\begingroup$ Thank you very much, kind sir. But what is the purpose of the circle? $\endgroup$ Mar 11, 2016 at 11:36
  • $\begingroup$ @Radoslav.Ivanov: I have no idea about the purpose of the circle/ellipse. Also, my answer is just a guess; there might be better answers that also explain the ellipse. $\endgroup$
    – Gamow
    Mar 11, 2016 at 11:54
  • $\begingroup$ Also can you explain the relation between the numbers, because as I understand it the equations c = da - b/a, so d = bc - b/a which is not 9... $\endgroup$ Mar 11, 2016 at 12:17
  • $\begingroup$ But the equation c=da-b/a yields d=(b+ac)/a^2. In the left picture this means 9=(8+2*14)/4, and in the right picture this means d=(15+3*4)/9=3. $\endgroup$
    – Gamow
    Mar 11, 2016 at 12:25
  • $\begingroup$ With only 1 complete sample we could make many relations fit. Like a+b+c+d=33, which makes the answer 11. There's gotta be something something else, like the circle, that determines the right answer. $\endgroup$
    – Kruga
    Mar 11, 2016 at 13:49

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.