Question 57861
this equation can be calculated the same way we calculate simple interest. 

use the equation a=p+prt

where p is the principle amount r is the rate of decrease and t is the time in years. and A is 0

substitute the values in for the equation

0=27600+(27600)(r)(12)

subtract 27600 from each side

-27600=(27600)(r)(12)

divide both sides by (27600)(12) to isolate r
-27600/(27600)(12)=r

r=-0.08333333

or r is 8.33333333% decrease per year