Question

When draining her hot tub, the height of the water in Brittany’s hot tub decreases at a rate of 2 inches per minute. After 9 minutes there are 11 inches of water in the tub. Assume that the height is decreasing at a constant rate.
a. Write an equation for the height of water left in the tub (h) as a function of the number of the minutes (t) that have elapsed.

b. What values of the domain, t, make sense? Why?

c. What values of the range, h, make sense? Why?

Answer 1

Step-by-step explanation:

a.

Let's give the starting amount of water as s. Every minute, 2 inches of water are lost, meaning that given the starting amount, s, we subtract 2 inches from s every minute, so s - 2 every minute = height of water left, so s - 2t (t representing minutes) = h

To figure out s, we simply plug our known value -- 9 minutes in and 11 inches left. s - 2(9) = 11, s-18=11, s= 29

29 - 2t = h

b. We know that we cannot have negative minutes, so the minimum amount of time that makes sense is 0. To figure out the maximum, we stop counting how much time has occurred when there is no water left, so we have to figure out when h = 0

29-2t = h = 0

t=14.5

Therefore, anything between 0 and 14.5 minutes makes sense

c. Anything between 0 and 29 makes sense because the height of water cannot be negative and we cannot get higher than the starting amount