Code Breakers! - Addition / reasoning about numbers

The worksheet that keeps on giving. Here is a sheet which provides a code breaking activity where pupils must use addition strategies and reasoning about numbers to make the totals given for each row and column. It is provided at three levels - 2x2, 3x3 and 4x4. A good challenge for all year groups from year 1 to 6.
It is made in Excel so just hit F9 when you have used it once and all the codes will be changed so you can use it again and again without having to work any thing out for yourself.