I am remaking the ITPs so that they will work on all modern browsers and tablets. They will remain freely available to all without the need for a subscription. This ITP shows two containers, holding different-coloured liquids, to model ratio and proportion. Each container has its own tap, which can be set to deliver liquid in units of 1 to 10.  A main tap can be set to deliver multiples of the amounts on the left- and righthand taps. Proportion can be modelled using the drain container, which receives whatever is in the left- and right-hand containers. Each container has a drain tap, which delivers the liquid into the drain container. The two liquids stay separated, so that you can measure the total amount of liquid and the individual proportions.