Odd One Out

Here are five different shapes. The question is simple. Which is the odd one out?

See if you can figure it out. The answer is given on the next page.

This puzzle comes from the Maths Blog of Tanya Khovanova, and we thank her for permission to reproduce it here.

The answer is that the Odd One Out is the only one that is NOT an Odd One Out! Which therefore makes it THE Odd One Out. If you see what we mean!

One of the contributors on Tanya's Blog puts it this way -

  • The second one says - I am special - I am the only one without a frame.
  • The third one says - I am special - I am the only one that is not square.
  • The fourth one says - I am special - I am the only one that is not red.
  • The fifth one says - I am special - I am the only that is small.

So it must be the first one, because it canít say that it has any special attribute not shared by at least one other object in the array.

Another contributor to the blog puts it this way.

  • Letís take the objectís properties for the set:
  • Object P1 P2 P3 P4
  • 1 red square framed big
  • 2 red square not-framed big
  • 3 red not-square framed big
  • 4 not-red square framed big
  • 5 red square framed not-big
  • letís assign a one code to the positive property and a zero to its composite value
  • Object encoded-value
  • 1 1111
  • 2 1101
  • 3 1011
  • 4 0111
  • 5 1110

We can see the zero value moving from the right to left so the sequence of objects follow a negative-property shifting from the right side to the left.

The best candidate to be out is the first object because it breaks above sequence, obviously due to it hasnít any positive property/

Tanya points out that she was inspired by the work of the late Martin Gardner, in creating this puzzle.

If the puzzle has piqued your curiosity, then have a look at this one...