 This is a mathematical snack from the Association of Teachers of Mathematics. This is a challenge using the digits 1 through to 9. I'm going to place each of my digits, which I've got stored at the top, onto this 3 by 3 grid. I'm going to put the 1 there, 2 here, 4. I'm going to put there, 3 I'm going to put here. You can put them anywhere you like. 7, 8, 5, 6, and then the final digit, 9, I'm putting on the top left-hand corner there. I'll put my 9 digits on the square. I'm using those digits to form numbers. Firstly, I'm going to form the numbers on each row, and this one here is 965. Using these digits, I get the number 378. Using these digits, I get the number 124. So you can see where I've got them from. There we go. I'm now going to add those numbers together to the total. 1, 4, 6, 7. There we go. I'm going to form another 3 numbers, and this time, I'm going to form them from the columns. 931. 672. And finally, 584. And I'm going to add those together, and I get 2, 1, 8, 7. And now I've got 2 totals. I'm going to take each of those totals, and I'm going to find the difference between them. So I'm subtracting now. The difference between the two totals is 720. Your challenge is to find the largest possible difference, and if you get that, why not try the smallest difference?