Maths Investigation - Opening a Lemonade Stand

This idea came from a game online where pupils get to choose which ingredients to buy. I found the online game to be a bit too complicated (and it uses dollars) so I made my own 'worksheet' that allows pupils to work in groups to decide how much of which ingredients to buy. They finished pretty quickly so I told them, once they had made a profit, to go back to the shop and buy more ingredients and see if they can make even more money. This quickly became a competition and everyone enjoyed it. Please give me some feedback on this, as I am a student teacher and would value all feedback.