Lesson 28. Number Tiles

A simply stated problem unfolds into a world of mathematics adaptable to a wide range of students. The problem: nine tiles numbered 1 through 9 and a 3 x 3 grid. Place the tiles in the first two rows of the grid to make three digit numbers. Now place the tiles remaining in your hand so that the three digit number they form is the sum of the other two.

There are many solutions. As a puzzle, finding one or even several solutions provides plenty of practice in basic arithmetic skills. However, the challenge of finding and justifying all 168 solutions elevates the puzzle into an extended investigation with a shift from arithmetic to concepts of strategy and proof.