Let me explain this rule by taking examples
1) 234163*11 = 2---2+3---3+4---4+1---1+6---6+3---3 = 2575793
Means insert the sum of 2 successive digits and put 2 terminal digits in its place
2) 45345181*11 = 4---4+5---5+3---3+4---4+5---5+1---1+8---8+1---1 = 498796991
Example.
Here an extra case arises
Consider the following examples for that
3) 473927*11 = 4+1--- (4+7-10) +1--- (7+3-10) +1--- (3+9-10) +1--- (9+2-10)--- (2+7) ---7 = 5213197
4) 584536*11 = 5+1---(5+8-10)+1---(8+4-10)---(4+5)---(5+3)---(3+6)---6 = 6429896