Lesson 18Using Water Efficiently

Learning Goal

Let’s investigate saving water.

Learning Targets

  • I can answer a question by representing a situation using proportional relationships.

Warm Up: Comparing Baths and Showers

Problem 1

Some people say that it uses more water to take a bath than a shower. Others disagree.

  1. What information would you collect in order to answer the question?

  2. Estimate some reasonable values for the things you suggest.

Activity 1: Saving Water: Bath or Shower?

Problem 1

  1. Describe a method for comparing the water usage for a bath and a shower.

  2. Find out values for the measurements needed to use the method you described. You may ask your teacher or research them yourself.

  3. Under what conditions does a bath use more water? Under what conditions does a shower use more water?

Activity 2: Representing Water Usage

Problem 1

Continue considering the problem from the previous activity. Name two quantities that are in a proportional relationship. Explain how you know they are in a proportional relationship.

Problem 2

What are two constants of proportionality for the proportional relationship? What do they tell us about the situation?

Problem 3

On graph paper, create a graph that shows how the two quantities are related. Make sure to label the axes.

Problem 4

Write two equations that relate the quantities in your graph. Make sure to record what each variable represents.