skip to content

Summer Maths Puzzles - Wednesday 28 August - Doors to your Destiny

​​Doors to your Destiny

  1. You are imprisoned in a land where analytical reasoning is prized more highly than guilt or innocence.  The prison guard brings you to 2 green doors A and B with signs on them and truthfully tells you that for all pairs of green doors you may encounter, the sign on one door is true and the sign on the other is false. 

  1. Having successfully avoided death in the first challenge you proceed along the corridor only to find yourself facing a pair of blue doors. The guard truthfully tells you that for blue doors, the signs are either both true or both false.

Which door do you choose?

  1. Having avoided death once more you proceed along the corridor only to find yourself facing another pair of blue doors.

Again, which door do you choose?


Entry to this puzzle is now closed.  Congratulations to the following for some great answers: 

  • Patrick Luo
  • Krishi
  • Alex Bell
  • Richard Hibbs
  • Mella Gallagher
  • Evgeny Mirkes
  • Ali Raad
  • Emily Lies and Jan Ricken
  • Manuja Isaac
  • The Koenig Family
  • Soham Sud


> Click here to return to the Summer Maths Puzzles homepage.

University of Cambridge Research Councils UK
    Clay Mathematics Institute London Mathematical Society NM Rothschild and Sons