What was the electric consumption last month?

Question

A company charges a base rate of $20 per month plus a supply charge of 9 cents per 1 kWh. What was the electric consumption last month if the months bill shows $104.60 in charges?

Answer 1

Let x be the number of kWh, and y be the monthly bill in cents

 

y(in cents)   2000      2009     2018 ...      10060        

 

x(in kWh)    0           1           2     ...

 

 

The equation that describes this table is y = 9x+ 2000

10460 = 9x + 2000

8460 = 9x

x=940

Last month the electric consumption was 940 kWh.

 

Answer 2

1.  Lets turn this into an equation.  $20 (base rate per month) + $0.09X (per kWh) = $104.60.  Now, we find x.

2.  Subtract $20 from each side:  $0.09X = $84.60

3.  Divide each side by $0.09:  X = 940

4.  940 kWh of electric consumption.