The bird population on an island is declining at a rate of 1.7% per year. the population was 4600 in the year 2009. which answer is the best prediction of the population in the year 2015?
4080
4010
4150
4120

Here is the  
A reduction of 1.7% will mean that 98.3% will remain. 
so, reduction factor of 0.983/year 
=> A(t) = A(0) x (0.983)^t 
Then, after 6 years we have: 
A(6) = 4600 x (0.983)⁶ => 4150 
Therefore, the answer for this would be the third option. Hope this helps.

The scale factor of what ?