One of my main responsibilities in teaching Year 3 Maths is to introduce 'Addition and Subtraction with Trading.'
it's hard to find games that involve trading, but I have managed to find this excellent interactive that allows you to approach these number problems online.
The NSW Department of Education and communities has an information sheet on how to trade.
The Junction Primary School (Newcastle, NSW) has an amazing list of online resources, comes highly recommended!
Maths Builder is fantastic as it encourages students to use working out paper and then answer the questions in the computer.
