How to work out the difference between 79 and 82 by counting on, demonstrated using candles on a cake. An ant has 79 candles. She needs 82 to put on the Queen's birthday cake. Her friend asks her how many more she needs. She works out that she needs 3 more by counting on from 79 to 82. She puts her 79 candles on the cake and her friend gives her 3 more, which she places on the cake to make 82.
What does 'counting on' mean? Find a specific number on the apparatus. "If we counted on 3, what would we get to?" Pause the clip at "we have 79 here and we need 82". Ask the children how many more candles are needed? See the different ways they work it out, then show the clip further. At a birthday party there has been a mistake, there have been the wrong amount of items ordered eg 4 less candles, 5 less napkins, plates, forks and so on. The children need to find out how many more items are needed. This can be done as a whole class where each group takes on an item or the children can calculate the mistakes in pairs or groups of things.