# Thread: Assistance with application problems

1. ## Assistance with application problems

Any help will be appreciated

The number of cases of a certain infectious disease reported in the united states can be modeled by D(t)=225(0.743t) thousands cases t years after 1997.
A) what was the average rate of change of the number of cases between 1997 and 2003?
B) Find the average number of cases reported in the USA between 1997 and 2003.

2. Originally Posted by Sundevils
Any help will be appreciated

The number of cases of a certain infectious disease reported in the united states can be modeled by D(t)=225(0.743t) thousands cases t years after 1997.
A) what was the average rate of change of the number of cases between 1997 and 2003?
2003 is 6 years after 1997. so the average rate of change is given by: $\displaystyle \frac {D(6) - D(0)}{6 - 0}$

B) Find the average number of cases reported in the USA between 1997 and 2003.
i suppose the average is per year? i further suppose we are considering 1997 and 2003 inclusive. it's just $\displaystyle \frac {\mbox{Number of cases reported between 1997 and 2003}}{\mbox{Number of years between 1997 and 2003}}$, which amounts to $\displaystyle \frac {D(1) + D(2) + ... + D(6)}6$