This is a great little investigation which has plenty of extension possibilities for those with enquiring minds. Dom the Dragon is thinking of a number and we are given two rules about the number: 1. The digits add up to 5. 2. None of the digits is a zero. The challenge is to find all the possibilities that the number could be. Write them all down, but make sure that the same numbers are not repeated. Some of the answers are immediately obvious, such as 14 and 41, but there are several 4-digit possibilities. Encourage children to set out their answers in the best possible way which will make it easier to see if all the possibilities have been found. There are several ways that this can then be extended. e.g. What would happen if the total added up to 6? What would happen if one of the digits was a zero? What would happen if a decimal point was used?