Tuesday 29 December 2009

A Christmas Puzzle.

As it is Christmas, here's a little puzzle to get the little grey cells in your brain working.

Study this diagram carefully.

There are two rooms side by side in a corridor. Room A and Room B.

You are in Room A. You cannot see Room B or what is in it.

Room A has three electric switches on a table - switch 1, switch 2 and 3.

Each switch connects to a light bulb in Room B. But you do not know which switch connects to which light bulb.

Your mission, should you choose to accept it, is to identify which switch connects to which light bulb.

You are only allowed to visit Room B ONCE only. That is the time when you identify which light bulb connects to its correct switch.

Once you leave Room A you cannot go back there - you have to go to Room B to identify the light bulbs.

How do you do it?

Answers in the comments box below. Thanx. Happy thinking.

P.S. I'll post the answer in the comments box shortly. Good luck!


  1. I have no idea what the answer is. I'm completely baffled! Cathy

  2. Hi Cathy,

    I'll give the answer here in a day or two.

    God bless.

  3. I dunno, I'll have to ask my six-year-old ;)

  4. She said lightbulbs don't work on tables, you have to put them in lamps :)

  5. Hi Mary,

    Lovely answer from your six-year-old. She's very clever.

    I could not draw three table lamps - that's why I put just the light bulbs. I'll give the correct answer here tomorrow.

    God bless you and your family.

  6. I reckon you start by switching on two of the three switches. If you've struck lucky and the visit to room B shows 2 lamps lit, then obviously the 3rd switch must relate to the unlit lamp.
    If only 1 lamp is lit then you can work out which the others are by logic . . . but I'm still working on that part!!!!!!
    On the other hand, that might not even be the correct initial step! I shall have to refer to my mathemetician son!

  7. Hi Miss Ellen,

    You're getting there. If you turn ON two switches and go to the next Room you'll find two lights ON. Now you know that the light which is OFF is connected to the switch you did not touch.

    But how do you know which switches connect to the other two lights which are ON. You can't go back to Room A once you leave it.

    I can assure you all three lights are connected to the three switches. So if you turn ON all three the three light bulbs will light up.

    Thank you for trying. My answer here tomorrow.

    God bless.

  8. Haha happy new years to you as well Vic.
    I'm really not good at these things. So I'll just have to wait for the answer lol

  9. Hello again, Victor. I've been thinking about this again & trying a different approach . . .
    I switch on 2 lamps and after a while I switch off 1 of them. Then I go into room B and see which lamp is lit, which is off but warm & which is cold. Am I getting any nearer?

  10. Miss Ellen - you are brilliant. Well done. You got it right.

    First you switch ON switch No. 1 for about ten minutes or so.

    Then you switch No 1 OFF - and switch No. 2 ON.

    Go to Room B.

    The lit lamp is connected to switch No 2.

    The warm lamp is connected to switch No. 1.

    The cold lamp is connected to switch No. 3.

    Well done. If it is any consolation I did NOT get the answer right when I first was given this problem. So you are more clever than me.

    God bless.

  11. Woohoo!! I couldn't sleep last night until I'd thought of another solution - and I didn't even have to wait until our younger son came up with the answer so maybe I do still have a few 'little grey cells' left after all :0)

    Wishing you all the Best for 2010.

  12. Hi Miss Ellen,

    Yes, your grey cells are working well. Well done for solving the puzzle.

    May I remind you that Father Ignatius stories will return on this Blog in the New Year.

    God bless you and your family throughout the New Year and always.

  13. Never even thought of that! I'll have to tell Michaela what the answer was, she's been curious. So have I :)

  14. Hi Mary,

    I couldn't get the answer right when I first was told this puzzle. It is logical when you think of it; and you're told the answer!

    God bless you and Michaela.

  15. I recently came accross your blog and have been reading along. I thought I would leave my first comment. I dont know what to say except that I have enjoyed reading. Nice blog. I will keep visiting this blog very often.



  16. Hello Lucy,

    Nice to see you visiting here. Thanx for your kind comments.

    God bless.



God bless you.