1 2 3 4 5 6 7 8 9 = 100

In the run up to my viva last week I became obsessed with a game I played a few years ago whilst at a summer school in Switzerland. Viva revision is somewhat mind-numbing because you feel that you are just reading your thesis thing over and over again. I took plenty of breaks to keep myself sane but I found that I needed to keep my brain active or I’d lose the plot. This game is the perfect coffee-break pastime when you need to stay alert.

Take the numbers 1 2 3 4 5 6 7 8 9 and make them equal 100 by placing any mathematical symbols you like between them. Any symbols are fine – I have yet to attempt using any of the numbers as indices, but that’s fine too. You must keep the numbers in the same order but you can combine them into larger numbers (e.g. 12, 56, 789) or chop them up using decimal points (e.g. 2.3, 7.8). As examples here are three possible solutions to show you how it works:

123 – 45 – 67 89 = 100
1 x 23 x 4 – (56/7) / 8 9 = 100
1 2.3 – 4 5 6.7 89 = 100

There are well over 100 solutions to this which means it is a game filled with multiple victories. Enjoy!