Answer:

It is a varying rate of change because the change in the number of cells varies from day to day.

Teacher Notes:

Students should have opportunities to study situations representing different patterns of change—change that occurs at a constant rate, such as someone walking at a constant speed, and change that occurs at an increasing or decreasing rate, as in a growing plant.10

10 National Council of Teachers of Mathematics (p. 163). (2000). Principles and standards for school mathematics. Reston, VA: Author.