A hot air balloon descends to the ground. The function a(t) = 210 – 15t can be used to describe the altitude of the balloon as it approaches the ground. The time is in minutes. What does t represent? What does a(t) represent? What information will a(5.5) give? A hot air balloon descends to the ground. The function a(t) = 210 – 15t can be used to describe the altitude of the balloon as it approaches the ground. The time is in minutes. What does t represent? What does a(t) represent? What information will a(5.5) give?