Engineers use mathematics every day and we’re so used to working with numbers that we often forget how much fun and often mysterious these numbers can be. In days gone by mathematicians would often earn extra money by performing stage tricks and one of the most amazing to those who saw it was the mystery of the number 1089.

The magician would stand at the back of the stage facing the audience with a slate in his hand. At the front of the stage would be a blackboard that only the audience could see. A member of the audience would be invited up onto the stage, let us call him John, and the magician would ask him to think of any three digit number where the first and last digits differ by two or more.

After writing the number on the blackboard with a piece of chalk for all to see the magician would then ask John to reverse the number and subtract the smaller from the larger. For example, if John’s number was 254, reversed it is 452 and 452 – 254 = 198. John would then be asked to reverse this new number and add the two together. So, 198 reversed is 891, and 891 + 198 = 1089.

Depending on how dramatic the magician wanted to be he could perhaps ask the audience to stare at the answer written on the blackboard and try to project it into his mind. He would then write the answer down on his slate and hold it up for the audience to see, usually drawing gasps of amazement from the crowd, as on the slate the magician would have written the number 1089.

Of course, our magician could only perform the trick once at any one time as applying the above procedure to any three digit number will always yield a result of 1089. Try it and see. Maths is fun! Of course though, there is no real mystery and to mathematicians the puzzle is little more taxing than adding up the weekly shopping bill. We’ll publish an explanation in the next issue of Motor Technology News.