Math Tricks

[Gaijin]

Do you know any of calculation tricks.

Here is a one that I know.
Take any 3 digits number, where the first digit is higher then the last digit. (321)
You then subtract the reverse number from the first one. (321 - 123)
And then you tell me only the last number of your result and I will tell you the whole result.

How does this work (Click to View)

Example: 632 - 236 = 396
As you see the first number is 632, 6 is higher then the last (2)
When subtracting a 3 digit number with it's on value reversed, the result has always the same effect
Example: 632 - 236 = 396 | 3 + 6 = 9
Example: 772 - 277 = 495 | 4 + 5 = 9
Example: 482 - 284 = 198 | 1 + 8 = 9
As you can see every of the above 3 results has a 9 in the middle.
When a person tells you the last number only, you just need to calculate 9 - x and the result is the first number.
3 + 6 = 9