A combination of different coins is used to make 50p to pay at a car park. Bill pays at a machine to park the car. One at a time, he puts in 5p, 5p, 10p, 10p, then 20p to make 50p. After each coin is put in, he adds up the total so far.
This clip is a useful introduction to systematic recording of all possibilities. Ask the children how many coins were placed in the machine (6 coins). The machine only accepts silver coins. Can the children list all the possible ways that it is possible to make 50p using only silver coins. How can you be sure you have got them all? By recording each possibility on a separate small card, children can then be encouraged to sort their cards into an order which convinces their partner they have got them all. Another investigation which draws on the need to be systematic is ‘half time scores’. The score at full time is 2-2. Can the children find all the possible half time scores. Again it is useful to record each on a separate card. This can then be extended to 3-3, 4-4 and so on.