Chapter 2: Properties of Real Numbers

#3001 Searching for Water on Mars - If we can find water on Mars, then astronauts won't have to take it with them. But how do you find the water before you send a manned mission?

Ask students to look for examples of mathematics as they watch Futures Channel Movie #3001.  In subsequent discussion, ask students if they think it is important for rover designers to know what the temperature will be on Mars, and why.  Elicit or present the fact that materials expands as they heat up and contract as they get colder, so it is important to know how much the temperature changes.  Then ask students to work in pairs to answer this question: The temperature on Mars can range from minus 140^o Fahrenheit to plus 95^o Fahrenheit. How would you find the difference between these two temperatures?

After a few minutes, accepts a few answers, then tell students that in this chapter they are going to learn more about how to carry out computations involving negative numbers. 

Note: Students sometimes have difficulty with the concept of negative numbers because they don’t see how something can be less than zero.  The problem may not be a misconception about negative numbers, it may a misconception about the meaning of zero.  To clear this up, help students to understand that the word zero means two different things: 1) Nothing and 2) A reference point on a scale, or a reference location.