Killer Sudoku Pro ups the ante on regular Killer Sudoku by adding even more types of operation into the mix!
Just like any other Sudoku, you must place each of the numbers 1 to 9 into the rows, columns and bold-lined 3-by-3 boxes - but you must also place numbers in each dashed-line cage so that the given total results when the stated operation is applied between all of the numbers in the cage. For subtraction and division you should start with the largest value in the cage and then subtract/divide by the rest.
There's just one more important rule: you cannot repeat a number within a cage.
As an example of how the puzzle works, consider the cage at the top-left of the example puzzle (on the right) - it must add up to 19, since the total is "19" and the operation is "+". The "120x" cage to its right must result in 120 when all the numbers in it are multiplied. Although this may seem like it would involve some slightly complex maths, in practice various logical deductions are all that is needed and you almost never need to calculate any large mathematical totals when solving.
There is only ever one possible solution, and it can always be reached by sensible logical deduction.