1. A helium balloon was let loose from San Francisco, California, which is at sea level. It rose to 10,000 feet and was carried eastward by the winds. Then it lost 4,720 feet of altitude and came down in Denver, Colorado. How high is Denver?

5. How do we solve this problem? Think of the height of the balloon as a number line where “up” is positive and “down” is negative 10,000 Ft Sea Level

6. 10,000 Ft Sea Level How do we solve this problem? Start at zero and add 10,000

7. 10,000 Ft Sea Level - 4,720 Ft How do we solve this problem? Start at zero and add 10,000 Now subtract 4,720

8. 10,000 Ft Sea Level - 4,720 Ft How do we solve this problem? Start at zero and add 10,000 Now subtract 4,720 What is the difference?