
kWh Costs Question

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.
