SOLUTION: an electric utility company charges residential customers 11,5 cents per kilo-watt hour plus a base charge each month.1 customer's monthly bill comes to $51,65 for 380 kilowatt hou

Algebra ->  Linear-equations -> SOLUTION: an electric utility company charges residential customers 11,5 cents per kilo-watt hour plus a base charge each month.1 customer's monthly bill comes to $51,65 for 380 kilowatt hou      Log On


   

Question 1027656: an electric utility company charges residential customers 11,5 cents per kilo-watt hour plus a base charge each month.1 customer's monthly bill comes to $51,65 for 380 kilowatt hours.Find a linear function that describes the total monthly charges for electricity if x is the number of kilowatt hours used in a month ?
Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
Plot monthly charges, +C+, in cents, on the vertical axis
Plot number of kilowatt hours used per month, +x+
on the horizontal axis
----------------------
+11.5+ cents / kWh is the slope of the line
----------------------
( 380, 5165 ) is given as a point on the line
( note that I converted the cost to cents )
----------------------
Use the general point-slope formula
+%28+C+-+5165+%29+%2F+%28+x+-+380+%29+=+11.5+
+C+-+5165+=+11.5%2A%28+x+-+380+%29+
+C+=+11.5x+%2B+5165+-+11.5%2A380+
+C+=+11.5x+%2B+5165+-+4370+
+C+=+11.5x+%2B+795+
---------------------
check the answer:
( 380, 5165 )
+C+=+11.5x+%2B+795+
+5165+=+11.5%2A380+%2B+795+
+5165+=+4370+%2B+795+
+5165+=+5165+
OK
( note that if no electricity is used, you still pay $7.95/month )