Paula found a partially completed table that her friend Donna was using to determine how fast water evaporated from a bucket during the summer. Every other day she measured the height of the water remaining in the bucket in centimeters.  

1. Review the Math Notes box in Lesson 1.1.2. Is this a proportional situation? If it is proportional, is it increasing or decreasing? If it is not proportional, explain why not.

   Hint (a):

   Proportional (or Direct Variation) situations have two requirements:
   1) The relation must be linear (increasing or decreasing).
   2) The linear relation must pass through the origin.

2. Complete the table.

   Hint (b):

   Looking at the completed days on the chart, by how many cm does the water level reduce every two days?
   Use this pattern to fill in the chart.

3. For this table, what is the rate of change, including the units? What is the unit rate of change?

   Hint (c):

   If the water level reduces by $3$ cm every two days, by how many cm does it reduce each day? (It is reducing, so remember that the slope will be negative).

4. Write an equation to represent the height of the water after any number of days.

   Hint (d):

   Substitute the slope and the water level when $x = 0$ into the equation of a line.

   Answer (d):

   $y = −1.5x + 30$