Playing Four Small Killer Sudoku Grids
The rules are those of every killer sudoku: each row, column and 2x2 box holds the digits 1 to 4 once, and the digits of a cage add up to the small number in its corner, without repeating. On a sheet of four, the grids are small, so write candidates sparingly: in a 4x4, many cages already tell you which digits they hold, a pair of cells of sum 3 being 1 and 2, and one of sum 7 being 3 and 4.
Easy, Medium and Hard Sheets
An easy sheet suits a first try: two digits are already written in each grid, and the cages hold two or three cells. A medium sheet removes the given digits, so the cage sums carry the whole puzzle. A hard sheet groups the cells into longer cages, where a sum of 10 over four cells says only that the cage holds 1, 2, 3 and 4, and the order has to come from the rows and boxes around it.
Using the Sheets in Class
Four grids per sheet give each student a short series to finish at their own pace, and the numbering of the sheets lets a teacher hand out the same one to a whole group. The sheets print on A4 in black and white.