The lost number

The Chinese are incredible with the numbers, although somehow it seems that they do everything the other way around, like their writing. It seems that they do the sums subtracting and the divisions multiplying. They are very good in mental arithmetic and make strange calculations through rules or tricks that cannot or do not want to explain.

One of his teachers taught me some amounts of sums that, in his peculiar Chinese way, invested to do them through subtraction and working from behind to forward from the response to obtain the figures that were added.

He asked me to order the nine numbers: 1, 2, 3, 4, 5, 6, 7, 8, 9 and another figure that I chose in a sum of two rows, to add them and then erase both both ads and one of the numbers of the result and that he would rebuild him. On the board you can see what was left after following his instructions.

Although the real riddle is simply to say What is the mysterious figure Could you put back the 10 disappeared digits?

Like all the added figures Dan 45, whose figures in turn add 9. We know that the sum of any combination of these figures used only once, it must be equal to 9. Since 1 + ? + 1 + 3 + 4 + 1 = 10, the closest number whose figures add up 9 is 18, so we know that 8 (18 - 10) is the mysterious figure.