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  • 4 years ago

If the power company charges $0.12 per kWh, what is the total cost of running the toaster and the refrigerator for the 10 hour period? Show formula and work.

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  1. anonymous
    • 4 years ago
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    I came up with this E=Pt $0.12kWh = P X 10h P = 83kW but isn't it wrong ?

  2. anonymous
    • 4 years ago
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    The energy used is indeed given by your formula, E = P t. So if you put in the power drawn by your toaster and fridge (you didn't give it), which would be given in kilowatts (kW), then you would indeed get a quantity of energy measured in kilowatt-hours (kW h). You could then multiply by the price of that energy from the power company, which is given in dollars per kilowatt-hour, to get the total cost, in dollars. That equation would look something like C = E x R, where C = cost, E = energy, R = price. (I didn't use P for price because you already used it for power.) In cases like this, a little "dimensional analysis" can help. Consider the units of the quantities you have, and the units of the answer you want. You have power (units of kilowatts) and time (units of hours) and price (units of dollars per kilowatt-hour). What you want is total cost (units of dollars). How is it possible to combine the units of what you have to get the units of what you want? dollars = (dollars/kW h) x kW x h That will work. The kW by which you multiply will cancel the kW in the denominator of the fraction, and the h wil do the same for the hours, leaving you with just dollars. So that tells you you're going to want to be multiplying your price by a power and a time.

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