Einstein's Number Trick: Fun for All

There are many interesting number tricks, and, if you've followed my articles, I've written quite a few about such interesting numerical wizardry. When we attach the name Einstein to a number trick, however, the idea takes on an entirely different dimension, both literally and figuratively. If you are interested in some fun with numbers, try out the trick below on some friends and family, and by all means teach it to your kids, if you have any.

The Einstein Number Trick is as follows: take a piece of paper and write down the number 1089, fold the paper in half, and give it to the other person, without revealing what you have written. Tell the person to pick any three-digit number, making sure that the first and last digit differ by at least 2. Tell this person to reverse the digits and to subtract the smaller number from the larger number. Then have this person take the result of the subtraction, and add it to the result with the numbers in reverse. Then ask this someone to compare the final result with the number you wrote on the piece of paper at the start.

Let's run through this with an example. Suppose your friend picks 523. This number is acceptable since 5 and 3, the first and last digits, differ by 2. Now reverse this to get 325 and subtract this from 523. Now 523-325 = 198. Reverse 198 to get 891 and add to 198 to get 1089!

Pretty cool, no? I bet you can impress quite a few people with this one, especially when you tell them that it was one of Einstein's favorite math puzzles. The reason this trick works is a topic for another article--unless of course you care to begin working the proof out yourself. It's not really all that difficult and I can show it in a few lines. However, for the moment, I'd rather you have tons of fun playing this one on your friends at the next party. And you know what: nobody gets hurt with games like these. Enjoy!