What was the electricity consumption last month if the month’s bill shows $104.60 in charges?

Question

Elspark, an electric utility company, charges a base rate of $20 per month plus a power supply charge of 9 cents per 1 kWh. What was the electricity consumption last month if the month’s bill shows $104.60 in charges?

Answer 1

Let K = consumption in kWh  

 

The total bill of $104.60 is equal to a fixed charge of $20 plus 9 cents for each K.  So the equation is 

 

104.60 = 20 + .09*K

84.60 = .09*K

K = 84.60/.09 = 940 

 

So the consumption was 940 kWh

 

Check:  20 + .09*(940) = 20 + 84.6  = 104.60