Here is a superb plenary for a lesson about multiplying and dividing by 10, 100 and 1000. This resource consists of two files. The first is a PowerPoint presentation that runs a game of Who Wants To Be A Millionaire. The Second is an Excel Document that gives pupils a worksheet to record their successes and failures on. A nice alteration to the traditional format of the game is to not eliminate players once they get a question wrong. Instead, encourage pupils to use the worksheet to record the winnings they get from each question and then to total up their prize money at the end. A super resource and thanks to Ceri Reece for bringing this to my attention.