What's the next square?

enter image description here

It was extracted from an IQ test of Mensa. There is no trap except I don't know if it can be solved.

There's some French before the question:

Parmi les 5 figures proposées, laquelle prolonge la série ?

which translates to:

Of the 5 figures proposed, which extends the series?


The first figure has 5 sides. The second has 6 sides and 2 rows outside. Let's assume that this 2 rows are the number of sides to subtract. So the second figure would have 4 sides and the third would have 4 - 1 = 3 sides. In this sequence, we have 5, 4, 3 and expect the next number will be 2.
The answer "a" have 3 - 1 = 2 sides, so I think it's the answer.

  • $\begingroup$ So the square following the answer contains a rare two-sided polygon. $\endgroup$ – Tom Aug 31 '17 at 8:53

The pattern could be:

A normal figure has 5 corners. A better figure has +1 corner and a = sign in bottom right corner. A poorer figure has -1 corner and a - sign in bottom right corner.

The next figure could be


  • $\begingroup$ Sorry, somebody change the sentence, we don't search wich one could go with the others. The real sentence is what is the next square. $\endgroup$ – Crunchy_Artie Aug 30 '17 at 7:14

In the first three figures,

the total number of lines (edges of the polygon plus unattached lines in the corner) is equivalent to 2 mod 3, and all quadrilaterals are rectangles.

The only one of the options that conforms to the above is


  • $\begingroup$ I sit back and wait, anticipating that the other two options will be supported also. $\endgroup$ – Peregrine Rook Aug 30 '17 at 5:39
  • $\begingroup$ The lines in the corner are irrelevant. What counts is the number of sides in the polygon. The sequence is: 5, 6, 4, 5, 3, 4. Therefore, the next in the series is the only five-sided figure: c. Give me a minute, and I'll see if I can come up with a rationale for b. $\endgroup$ – Hugh Meyers Aug 30 '17 at 6:42

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

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