RATIOS

Murray, Richard Gage Park High School
Berwyn, Ill 60402

Objectives: The students are to examine models and compare their lengths numerically. The students will measure the models and will then calculate the length of the real size base on knowing what the scale of the model is. Apparatus needed: What is needed is models of real objects that are familiar to the student. I used models of the Space Shuttle (three models of different sizes) and "Matchbox" cars. This product has the scale written on the bottom of the car. Recommended Strategy: What I did was display the three models of the Space Shuttle. I asked questions about how to describe the models. I accept all answers but what I am looking for is a mathematical description such as "twice as large", "three times as big". I talked about numerical descriptions and how to write comparisons as ratios. I would take the ratio and write it in the form where the numerator is 1. I would then talk about scales and what they mean. What does it mean that 1 inch is to 88 inches.I would take the model of the car and knowing the scale of the model, project how big the car would be in reality. The students would then pace off the actual length, by counting the tiles on the floor in the classroom. Review with the students that the scale may be written in metric and not English units. The difference is that a scale based on metric system if it is written in English Units will result in a real figure that is much larger than the actual vehicle could be. The students need to have an understanding of what the actual size of the real object is. Most students know how large a car is, whereas they might not know what the actual size of a railroad engine is and its actual length.