Question

1. a particular portable air conditioner uses 1000 watts. what is the cost to run the ac for 1 hour, assuming 15 cents per kilowatt - hour?

options: 15 cents per hour, 150 cents per hour

1. a central whole - house ac might use about 4000 watts. what is the cost to run the ac for 10 hours in a day, at 15 cents per kilowatt - hour?

options: 60 cents, 600 cents

1. an electric fan uses very little electricity, perhaps 40 watts (in contrast to a central ac’s 4000 watts). at 15 cents per kilowatt - hour, how much does a fan cost to run for 10 hours?

Explanation:

Problem 1

Step1: Convert watts to kilowatts

The AC uses 1000 watts. Since 1 kilowatt = 1000 watts, we have \( \frac{1000}{1000} = 1 \) kilowatt.

Step2: Calculate cost per hour

The cost is 15 cents per kilowatt - hour. For 1 kilowatt - hour, the cost is \( 1\times15 = 15 \) cents.

Step1: Convert watts to kilowatts

The AC uses 4000 watts. So, \( \frac{4000}{1000}=4 \) kilowatts.

Step2: Calculate energy for 10 hours

Energy (in kilowatt - hours) for 10 hours is \( 4\times10 = 40 \) kilowatt - hours.

Step3: Calculate total cost

At 15 cents per kilowatt - hour, the total cost is \( 40\times15=600 \) cents.

Step1: Convert watts to kilowatts

The fan uses 40 watts. So, \( \frac{40}{1000} = 0.04 \) kilowatts.

Step2: Calculate energy for 10 hours

Energy (in kilowatt - hours) for 10 hours is \( 0.04\times10=0.4 \) kilowatt - hours.

Step3: Calculate total cost

At 15 cents per kilowatt - hour, the total cost is \( 0.4\times15 = 6 \) cents.

Answer:

15 cents per hour

Problem 2