KenKen - Mental Maths Brilliance!

Although it may look like just another Sodoku spin-off, don't be fooled! Kenken is a serious mental maths workout. Ok, so the example given above is it little simple, but you need to start simple to learn. 

The rules:

1. The numbers you can use in a puzzle depend on the size of the grid. If it’s a 3 x 3 grid, you’ll use the numbers 1–3. In a 4 x 4 grid, use numbers 1–4. In a 5 x 5 grid… well, you can probably figure it out from there.
2. The heavily-outlined groups of squares in each grid are called “cages.” In the upper-left corner of each cage, there is a “target number” and a math operation (+, –, x, ÷).
3. Fill in each square of a cage with a number. The numbers in a cage must combine—in any order, using only that cage’s math operation—to form that cage’s target number.
   Example: Your target number is 5, your operation is addition, you’re using the numbers 1–4, and the cage is made up of two squares. You could fill in 2 and 3 (because 2 + 3 = 5) or 1 and 4 (1 + 4 = 5). But which number goes in which square? Read the next instruction!
4. Important: You may not repeat a number in any row or column. You can repeat a number within a cage, as long as those repeated numbers are not in the same row or column.

This is fantastic to use as a mental maths starter. You can get as many different difficulties as you like from the KenKen site. Try getting year 6 to work up to solving something like this...

...and in the process enjoy the benefits of having a games-rich classroom.