Numeracy for the 21st Century requires more than skills and facts. It is well-recognised that numeracy is applying knowledge as required in everyday life. This highlights the centrality of applying mathematics in real-world contexts.
Proportional reasoning is the ability to understand situations of comparison. In the real world, this is a major aspect of many day-to-day tasks.
Making the perfect cup of tea by ensuring the tea-bag has been immersed for the right amount of time and the correct amounts of sugar and milk are added
Putting the right amount of washing powder into the wash for the amount of washing placed into the machine
Creating the perfect cordial and soda (or Gin and Tonic)
Sharing a large bottle of drink amongst 8 children
Adjusting recipes for more or less
Using non-standard measuring devices in measuring situations (hand-spans when you don’t have a tape measure; containers when you don’t have a measuring jug).
Underdeveloped proportional reasoning potentially impacts real-world situations, sometimes with life-threatening or disastrous consequences (e.g., administration of incorrect doses in medicine; inaccurate mix of chemicals in pesticides; failure to accurately convert between units of metric and imperial units of measure). A rich field of potential investigations for promoting numeracy opens up when one considers the multi-faceted and multi-dimensional nature of proportional reasoning.