The amount of a radioactive preporation y mg decreases by the formula
y=80*0.5^0.2t where t is the time in years after the start of 2000, what is the average rate of change between the start of 2005 and the start of 2007

I know am suppose to put the years into the calculation some place but from there am lost

2. Originally Posted by JBswe
The amount of a radioactive preporation y mg decreases by the formula
y=80*0.5^0.2t where t is the time in years after the start of 2000, what is the average rate of change between the start of 2005 and the start of 2007

I know am suppose to put the years into the calculation some place but from there am lost
the average rate of change for $\displaystyle y(t)$ from 2005 to 2007 is given by: $\displaystyle y_{avg}(t) = \frac {y(7) - y(5)}{7 - 5}$

can you continue?

3. ok tryed to work it , is the answer 10.31mg?

4. Originally Posted by JBswe
ok tryed to work it , is the answer 10.31mg?
i got a negative answer (which you should, since the sample is decreasing)