An electric water heater consumes 2.5 kW for 1.9 h per day. What is the cost (in $) of running it for one year if electricity costs 11.5 cents/kWh?

The cost of running the electric water heater for one year is 55.2391 $

Explanation:

The simple rule of 3 helps to quickly solve proportionality problems when you have three known values and one unknown. If two quantities are directly proportional (that is, when multiplying or dividing one of them by a number, the other is multiplied or divided respectively by the same number) the rule of three can be applied as follows:

a ⇒ b

c ⇒ x

So:

where a, b and c are the known values and x is the value you want to find out.

In this case, you can first apply the following rule of three: if 2.5 kW are consumed in 1.9 hours, in 1 hour how many kW are consumed?

kWh=1.316

So an electric water heater consumes 1.316 kWh in one day. You apply another simple rule of three: if the heater in 1 day consumes 1.316 kWh, in 365 days (1 year) how many kWh are consumed?

kWh= 480.34

So an electric water heater consumes 480.34 kWh in a year.

If 1 kWh costs 11.5 cents, 480.34 kWh how many cents does it cost?

cost= 5,523.91 cents

Finally, if 100 cents is equal to 1 dollar, 5,523.91 cents, how many dollars are equal?

cost= 55.2391 $

The cost of running the electric water heater for one year is 55.2391 $