A.10 Summation Basics
\(123 = 3 \times 1 + 2 \times 10 + 1 \times 100\)
- Value of a number depends on digits it consists of
Arrangements of 1, 2, 3
123
132
231
213
312
321
In all places, each digit is repeated twice (2!)
Sum = 2!(1+2+3)1+2!(1+2+3)10+2!(1+2+3)100 = 2!(1+2+3)(1+10+100)