Individuals conceptualize positive and negative integers in different ways. Today we investigated 3 possibilities. The first is a number line or thermometer. Take the example of 10 + (-5). The number line method suggests to start a 10 and pull back or drop down 5 steps or degrees. In either case, you stop at 5. Another way to think about it is looking at the absolute values. Again, our example of10 + (-5) = /10/ + /5/, find the
difference, which is 5, then ask - which integer (+ or -) has the higher value; in this case (10) is positive. Thus the difference; 5, and is positive. Finally, look at the values as positive and negative charges. Yes, using 10 + (-5):
 |
| Pictorial representation |
An important concept is: n + (-n) = 0. With n = any number.
A example given to the students was -25 - (-25). We've all learned the "trick" is to rewrite the expression as -25 + 25. Then the question was asked -- Why? What is happening? What real life example could represent this expression? After sharing possibilities and extended discussion, students were able to deduce that -25 - (-25) is indicating that (-25) is "taken away." Pretty good. Ask your child about the real life example(s).
 |
| Whole Class Practice Example: notice the steps. |
 |
| Homework due tomorrow, 10/23/14 |
