New Trick for Our Mathemagicians

Our newest math "magic" trick has to do with a very special number - 6,174. It is known as Kaprekar's constant, after the mathematician D.R. Kaprekar. What makes this number so mysterious?

Take any four digits, as long as they are not all the same. Write the digits to make the largest number possible. Then take the digits and make the smallest number possible. Subtract the smaller number from the bigger number to get your answer.

Is this answer 6,174? No? Well, let's do it again, because it WILL be!

Take your answer and do the same - make largest number, smallest number, and subtract smallest from biggest. Keep doing this until you get 6,174. You always will, in no more than 7 steps.

We will continue working on this at school, and it would be great to have your children show you at home as well. The magic for me is that it is a great way to give our students practice with subtraction with and without renaming!