Present students with this game - they are to use a calculator to check their answers initially. Play the game in pairs where students have to aim to place a counter in a cell on the game board by choosing two numbers which multiply to give that number. You want students to be looking for ways to work this out without the use of a calculator. You can then go on to discuss what students find, including that I have used powers of 10 here. Two different game boards are provided but you can easily change the numbers to give yourself new boards.