"Let's play mini-Sudoku!
We wish to place an "X" in four boxes, such that there is exactly one "X" in each row, column, and 2x2 outlined box. In how many ways can we do this?"
" Using constructive counting and combinations together, we can find 16 possibilities. This is how we find the answer: First, we determine how many possibilities there could be without any restrictions. We do this by choosing one possibility (as seen in the example) and calculating the number of spots you could place the "X" in the grid. In this circumstance -with 16 available slots- there are 384 possible combinations with over-counting. We have drastically over-counted so we divide by the number of X's in one solution factorial (24). When we divide by 24, we get 16 possible ways to solve a mini-Sudoku problem. Let's play!"