g you are shopping for a new refrigerator and the salesperson tells you get a better deal with the energy efficient model (because of more efficient compressor) even though it costs $1200 versus the standard model which costs $1005. Looking at the specifications, the energy efficient model uses 195 W whereas the standard uses 335 W. Also, because of better insulation. the energy efficient model runs 10% of the time versus the standard which runs 25% of the time. if electricity costs $0.12 per kWh, how long will it take to make up the difference in the cost?

It will take 1996 hours (83 days) to make up the difference in price.

Explanation:

Giving the following information:

Efficient model = 1200

Standard model = 1005

Price difference = $195

Efficient model = 195 Wh = 0.195Kwh (runs 10% of the time)

Standard model = 335Wh = 0.335Kwh (runs 25% of the time)

Electricity costs 0.12 an hour

Cost per hour:

Efficient model = (0.195Kwh*0.10) * 0.12 = 0.00234

Standard model = (0.335*0.25) * 0.12 = 0.10

Cost per hour difference = 0.10 - 0.00234 = 0.0977

cost difference = cost per hour * number of hours

195 = 0.0977*X

1996 = X

It will take 1996 hours (83 days) to make up the difference in price.