Question

12345=5,25752=8,35741=5,84239=?

Answer 1

Firstly, do addition of the digits in two pairs and we obtain same number. The one which is remaining follows (-1,+1,-1,+1) process.

Example in 12345 2+3 = 5 and 1+4 = 5 and number left out is 5 - 1 = 4.

so, in 84239 the answer is 5
8 +3=11 and 9+2=11
So number left out is 4+1=5.

5 is the answer.