Christmas MathDoku

Here are four MathDoku; or KenKen type puzzles. We've simplified the more traditional version so that this only includes addition. The idea is for the children to work in pairs to complete each 5x5 grid; following the simple rules: - the numbers entered into each 'cell' (squares marked out by darker lines) should total the clue number in the top left-hand corner; - only the numbers 1; 2; 3; 4 and 5 are used; - like Sudoku; numbers only appear on each row or column once. The handout here includes four KenKen puzzles (together with answers).