The last digit of any multiplication depends only on the last digit of each number being multiplied, and not for example, on the size of the numbers or their order.

\[3 \times 2=6\]

If the last digit of a number is 2 and the last digit of any other number is 3, the last digit of their multiple will be 6, so the last digit of  
\[53 \times 42=2226\]
  is 6. The complete list of posdible combinations of last digits is given in the table.

Number A\Number B 0 1 2 3 4 5 6 7 8 9
0 0 0 0 0 0 0 0 0 0 0
1 0 1 2 3 4 5 6 7 8 9
2 0 2 4 6 8 0 2 4 6 8
3 0 3 6 9 2 5 8 1 4 7
4 0 4 8 2 6 0 4 8 2 6
5 0 5 0 5 0 5 0 5 0 5
6 0 6 2 8 4 0 6 2 8 4
7 0 7 4 1 8 5 2 9 6 3
8 0 8 6 4 2 0 8 6 4 2
9 0 9 8 7 6 5 4 3 2 1