his bill is $113. When he uses 1,500 kilowatt hours of electricity, his bill is $153. What is the monthly administration fee?

Question

Bryan’s monthly electric bill is determined by adding a flat administration fee to the product of the number of kilowatt hours of electricity used and the cost per kilowatt hour. When he uses 1,100 kilowatt hours of electricity, his bill is $113. When he uses 1,500 kilowatt hours of electricity, his bill is $153. What is the monthly administration fee?

Answer 1

113 = 1100k + f

153 = 1500k + f

40 = 400k

k = .1 = 10 cents per kw

113 = 1100(.1) + f

f = 113-110 = $3 fee

153 = 1500(.1) + f

f = 153-150 = $3 fee