Divination Inference (Young Bao Qingtian 3) Episode 19

According to the meaning of the question (no way, the problem-solving model in high school has long been deeply rooted! ): "Choose a two-digit number at will (in other words, choose a number from 10~99 at will), add the ten digits of this number to this digit, and then subtract this sum from the selected number. For example, if the number you choose is 23, then 2+3=5, then 23-5= 18 "Let the ten digits of this two-digit number be X (0 < X ≤ 9) and one digit be (0≤y≤9), then this two-digit number is10x+Y. ..

Add the ten digits of this number to this number, and then subtract the sum of the previous demands from this number, and the result is = (10x+y)-(x+y = 9x.

Take 23 as an example, because the decimal digit X is bit 2 and the unit digit Y is 3, the result is 18, so according to (10x+Y)-(x+Y = 9x,

We can know that 9x = 18.

Then x = 2.

And the number on the unit, once again into the formula, you can know that y = 3.

That is to say, divide the number by 9 to get a ten-digit number, and then substitute it with a formula to get a digit number.

Very simple truth ~