Ratio and proportion – a key activity: links fractions, direct proportion, straight line graphs, map scales, currency and unit conversions, recipes and so much more. Bars used too to help show ratios.
Spire Maths Interactives for Ratio and Proportion (will not work on iPhones or iPad) found here. Wealth of material for KS3.
See also these Bar method activities, some of which include Ratio and proportion problems.