Question

For the past ten years, Michelle has been tracking the average annual rainfall in Boynton Beach, Florida by recording her data in the given table. She has concluded that the relationship can be modeled by a linear function.

Year 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013
Average Rainfall(in inches) 62.33 61.8 61.27 60.74 60.21 59.68 59.15 58.62 58.09 57.56
Based on the data provided in Michelle's table, use complete sentences to explain how the average rate of change in Boynton Beach's rainfall for the years 2004-2013 can be found. Use the data provided in the table to calculate the average rate of change in precipitation.
Use complete sentences to explain what the average rate of change means in terms of the average rainfall.

WRITER

Answer 1

To find the average rate of change from 2004 to 2013, compute the change in rainfall divided by the change in years (the slope of the line): rate = (rainfall in 2013 − rainfall in 2004) / (2013 − 2004). Using the table, rate = (57.56 − 62.33) / 9 = −4.77 / 9 ≈ −0.53 inches per year.

This means that, on average, Boynton Beach’s annual rainfall decreased by about 0.53 inches each year between 2004 and 2013 (a total decrease of 4.77 inches over the period).