## Thinking Mathematically (6th Edition)

a. $1.33$ c. $C=310+x*1.33$ b. $443$
a. To estimate the yearly increase in the average carbon dioxide concentration, in parts per million, we need to: 1. subtract the number from the first recorded year (1950) from the last recorded year (2010). 2. divide the result by the number of years between them. $390-310=80$ $80\div60\approx1.33$ (We're rounding the result to the nearest hundredth, as instructed in the exercise). The estimated average yearly increase is $1.33$ (parts per million). b. The mathematical model looks like this: $C=310+x*1.33$ C is the concentration of carbon dioxide. 310 is the value in 1950. x is the number of years after 1950 for which we are calculating. $1.33$ is the estimated average yearly increase. c. The average concentration in 2050, calculated with our mathematical model, would be: $C=310+(2050-1950)*1.33=310+133=443$