Nine days ago, the area cove by the mold on a piece of bread was 3 square inches. Today the mold covers 9 square inches. What is the rate of change in mold's area?

Answer: The rate of change in mold's area would be 2 square inches per day.Given that,The area cove by mold 3 days ago= 3 square inchesThe area cove by mold today= 9 square inchesChange in area= 9-3= 6 square inchesNumber of days during which this change occu= 3So,The rate of change in mold's area= change in area/number of daysThe rate of change in mold's area= 6/3=2 square inches per day.