On a particular day, the following appliances are used for the times indicated: a 1600-W coffee maker, 13 min, and a 1100-W microwave ?

Question

On a particular day, the following appliances are used for the times indicated: a 1600-W coffee maker, 13 min, and a 1100-W microwave oven, 3.9 min. With these power requirements, find how much it costs to use these appliances at an electrical cost of 9¢ per kWh. (Do not round your final answer

Answer 1

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That's pretty cheap for electricity and a really powerful coffee maker.

Do you want the approach, or just an answer?

Watts to Kilowatts, minutes to hours. Do that for each appliance.

Add the two kWhr together, and multiply by $0.09 

1.6 kW x 13/60  which is 1.6 kW x 0.2166667 = 0.3466667 kWh for coffeemaker

1.1 kW x 3.9/60 which is 1.1 kW x 0.065 =  0.0715 kWh for microwave

0.41816666667 kWh total

$0.03763500003

There are other ways to be more precise now that you see one way.

1.6 x 13 =  20.80  kW minutes

1.1 x 3.9 = 4.29 kW minutes

20.80 + 4.29 = 25.09 kW minutes

(25.09/60) x $0.09 

2.2581/60 kWh

$0.037635   << exactly