In previous sections, we use number lines with arrows to represent given statements. We also learned addition statements. In this section, we are looking at subtraction statements. A thermometer is just like a number line, except thermometers are vertical. As the line on a thermometer moves down, the temperature gets cooler and as the line moves up, the temperature gets warmer. In this section, the blue arrows on the number line will move to the left, or down the number line, and represent negative integers. The red arrows will move to the right, or up the number line, and represent positive integers.
George lives 15 floors up from street level in his apartment. He rides down the elevator from his room to a parking level that is two floors below street level. How many floors does he ride down in total?
The temperature recorded in Whitehorse, Yukon on Christmas day is -20 degrees Celsius. On the same day in Hawaii, the temperature is + 25 degrees Celsius. What is the temperature difference between these two places?