Answer to the Friday Puzzle….


On Friday I posted this puzzle.  This triangle is constructed from 10 coins.  What is the smallest number of coins that need to be moved to make the triangle point downwards?

If you have not tried to solve it, have a go now.  For everyone else the answer is after the break.

The answer is…..three!

Did you solve it?  Any other answers?

I have produced an ebook containing 101 of the previous Friday Puzzles! It is called PUZZLED and is available for the Kindle (UK here and USA here) and on the iBookstore (UK here in the USA here). You can try 101 of the puzzles for free here.

35 comments on “Answer to the Friday Puzzle….

  1. The answer was hinted at in my reply to the puzzle, 3 seconds.. 3 moves.

  2. Roland says:

    Just turn your monitor, or walk to the other side of the table. Then you need to move 0 coins…

    • Edgar says:

      I like this answer.

    • Repton says:

      If the triangle is flat on a table then it doesn’t point downwards, wherever you stand :-)

    • Berhard says:

      Had the same idea, but turnig the monitor would include that all coins where moved ….
      Walking around the talbe includes that the the coins are not arranged pointing downward… (rather forward or backward)….
      Flipping the whole universe.. includes moving all other coins…
      Just redefine upward as downward and downward as upward… than it is not even necessarry to walk around the table..

    • Emlyn says:

      No need to flip the whole universe, you just have to move the earth so that gravity points in the opposite direction!

    • Al Johnston says:

      … or tilt your head 60 degrees to one side ;-)

  3. Leszek Cyfer says:

    As I was doodling with bearing balls some time ago I came up with a figure that combines those two triangles (think of adding three circles instead of moving them). I realized then that it is the Star of David and there is a central circle which represents Messiah and then 12 circles surrounding it. This answered my never vocalized question why Jesus had to have 12 apostles.

  4. Simon says:

    Hang on, hang on. This solution doesn’t make sense. Which three from the top triangle are removed? Can the coins be numbered 1-10 to show where they end up in the answer?

    I’m so confused!

  5. Robot says:

    I don’t need to move any coins, or change the orientation. I simply add 18 coins to make the triangle point downwards (albeit creating a larger triangle).

  6. Anonymous says:

    Woohoo! I got it. Not too hard.

  7. fluffy says:

    I “got it” insofar as I already knew the answer for this is another puzzle that’s quite classic.

  8. nanda says:

    got it. may be 10 sec

  9. robert says:

    Got it fairly quickly, and for once, I must acknowledge the local church, where we go every Christmas for helping me with this puzzle. There is a stained glass wall with a similar circular pattern, and a picture of some biblical scene. I spent numerous hours trying to find the biggest triangles possible, and in what directions they could be made. Time well spent.

  10. Lazy T says:

    What are the other solutions people were claiming?

  11. The other Matt says:

    Nope, i thought that the triangle is made with balls, standing on a table and our job is to make to fall the triangle point downwards by removing balls.
    But which can be the triangle point ? In this case we have three of them.

  12. Ed says:

    I solved it in Excel.

  13. Jerry says:

    My reply on Friday also hinted at the solution. The central core of the diagram looks like flower with a center circle and six petal circles. Once you see that pattern, it is easy to see how the additional three circles on the periphery can be moved around to make the arrow point in the desired direction.

  14. Eddie says:

    I got 4 because, like a complete fool, I failed to take symmetry into account

  15. SeleneBlueSky7 says:

    For once I can say that I completely figured out this one! :-) Yep, three.

  16. spiderabc1 says:

    Turning myself (first answer) was not answering the question about moving the coins. 3 was my second answer, moving 2 then 1. I have seen it before though.

  17. Devi says:

    Solved it real quick! Think i’ve seen it before though….

  18. Zach says:

    it depends on your definition of “downward.” you didn’t say “straight downward”, so theoretically, you could keep it as is and have the left point of the triangle be the bottom.

  19. dshan says:

    hey , what are the maximum outputs for this puzzel ,like this is an example while n = 4 you get output as 3 , now what are possible outputs while n > 4 (5,6,7,8,9…..)?

  20. I am wanting to start my own business and need to know how to start a website for a cheap/free price.. I am looking to start my own photography business and want to get a website up. I am planning on using this for a way to let people know about me, give them different albams of an axample of my work and then a way to contact me. I would love for it to be cheap or free in order to get started..

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