Tuesday, 10 December 2013

Simple Elegance

I love maths that challenge us to think, but are deceptively easy at first glance so that they don't put children off.  This week, I gave Tiger one of these simple and elegant maths riddles that require a good understanding of:
  • mental calculation
  • addition
  • place value
  • numbers

The idea is to use the ten digit cards, as set out above, to lay out an addition equation visually in the vertical format.  A few rules to bear in mind:
  1. The digit zero (0) cannot be used on its own.
  2. The digit zero (0) cannot be placed in front of any number, i.e. it can't be used as "081" and such like.
  3. The addition sign (+) is assumed.
  4. The final number on the last line is the sum.
  5. No carry-overs are to be shown.
Easy, no?  For example, 76 + 80 = 156.  Each digit in the equation is selected from the set above.  The solution would be shown as follows on the table:


Or, if the equation is 25 + 66 = 91, the solution would be presented as:


All clear?  Ready to go?

The idea is to start with any combination using the set of ten cards as shown in the photo above, then slowly build up to using all ten cards.

Tiger quickly found numerous solutions using three to nine cards, but he struggles to use all ten cards in a single solution.  The game is too much fun to just sit and watch so I used a second set to play alongside Tiger, at which point it turned into a competition between us to see who could find the solution to the ten-cards problem first.  I am pleased to report that I have uncovered one solution to the ten-cards problem, although it did take me quite a few attempts.  I'm sure there is more than one answer to this problem.  Tiger hasn't found his solution yet.  His challenge is to find the solution by Christmas eve, while mine is to find at least one more solution by then.

Join in the fun if you feel inclined!  I'll post our solution(s) on Christmas eve.

This post is linked up to:
  1. Hip Homeschool Hop - 12/10/2013
  2. Math Activity Thursday
  3. Entertaining and Educational: Travel is One of the Best Ways to Learn
  4. Collage Friday - A New Camera and Birthday Happenings
  5. Weekly Wrap Up: The One Where I'm Still Not an Aunt
  6. The Homeschool Mother's Journal {December 14, 2013}


  1. There's nothing like a challenge to make kids think - and us too! Great idea.

  2. Thanks, Julie. I like it when things are simple. :-)

  3. This looks great. I thought I was missing something about why the digits are lined up the way they are in the sum that adds up to 156 but having puzzled over it with my husband just now we've decided it's just a matter of formatting! We'll give it a go - thanks! :-)

  4. Oops! I hope the place values show up properly in everyone else's browser! Maybe I'm not explaining the puzzle clearly... :-( Do let me know if you have further questions. I'll try my best to explain it better. Have fun!

  5. No your explanation was very clear, it was just me looking to over-complicate things, I think (ironically!). I'm very impressed you've found a 10 digit solution!

  6. LOL. Thanks for letting me know, Lucinda. I know what you mean. I did say the puzzle is "deceptively simple". I don't blame you for thinking, "Is that it?" :-)

  7. What a great maths activity for winding down to over the holidays. I'm definitely going to give it to my older ones to keep their mathematical minds agile!


Related Posts Plugin for WordPress, Blogger...