Scaling a recipe up or down your cookies were a hit at the Church meeting and they would appreciate it if you prepared a dozen batches for the bake sale in September. You have to use an equation to scale a single batch to 12 batches for a bake sale
Maps typically display a scale for distances you can use to equate to miles, time, through mph when you travel. Maps are typical examples of scale downs that are scaled up to let people calculate how long their driving trip will take. In fact when google for example "Get Driving Directions" you enter a starting address and a final address Google Maps, Navigation Programs in cars and other applications like Mapquest do the calculations for you.
Scaling, using Proportions (proportion say two ratios are equal) are used in Construction, Fashion Design (different sizes for the same piece of clothing) and Interior Design
Temperatures if you are from the US you are probably accustomed to temperatures in degrees F but temperatures are also expressed globally in Centigrade, Celsius, and even Kelvin there are equations that allow you to easily convert from one F to C.
English versus Metric units since things are more global than ever with increased internet use most people will need to know how convert units of measure for size within the English system that we use in the US and how to convert from English to Metric units and to do size conversions in the Metric system as well; These equations are just known as Conversion Factors
I hope this helps we use equations all the time for travel, building, understanding units of measuring, judging time and distances but the seem so common that we don't recognize that we are using them.
