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kWh Costs Question
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Look at the table of data below. For the hairdryer, notice that both power and time aren't always in the "expected" units of kW and h.
| Object | Power | Time used | Units used (kWh) | Cost (p) |
| hairdryer | 1·2 kW | 30 minutes | 0·6 | 4·8 p |
| light bulb | 100 W | 20 hours | | |
| microwave oven | 800 W | 45 minutes | | |
| Assume 1 kWh of energy costs 8 p |
For the hairdryer, remember that 60 minutes = 1 hour, so 30 minutes = 0·5 hours. We must use this to find the units (kWh) used.
See if you can work out the units used, and the cost of running, the light bulb and microwave oven.
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