Question 47587This question is from textbook Beginning Algebra 
:  Need help solving these kind of problems.  Once I am shown how to work this type, I will be able to work the rest.
 
The electricity costs of a business decreased from $12,000 one year to $10,920 the next. What is the rate of decrease?
 
 Can someone show me how to set up the problem to get the solution.
 
Thank You
 
 
This question is from textbook Beginning Algebra 
 Answer by Nate(3500)      (Show Source): 
You can  put this solution on YOUR website! The time it took to decrease the electricity cost is one year. 
(12000,0) and (10920,1) 
Now, find slope: 
M = (y2 - y1)/(x2 - x1) = (12000 - 10920)/(0 - 1) = -1080 
1080/12000 = 0.09 = 9% 
The Rate of Decrease: 9% 
Check: 9% of 12000 is 1080 .... 12000 - 1080 = 10920 
  | 
 
  
 
 |   
 
 |