An electric whisk in a bakery has two motors, each with an average power of 1500W. The whisk is used for 4 hours each day, 7 days a week. Electricity costs 18p per kilowatt-hour. Calculate the cost of the electricity used by the whisk in one week.

First, we must calculate the amount of time spent using the whisk in one week:4 x 7 = 28 hours a weekNext we calculate the power used; as the whisk has two motors, the average power used by the whole whisk is 1500 x 2 = 3000W. To convert this to kilowatts, we divide this number by 1000 which means total power is 3kW.The number of kilowatt-hours is simply calculated by multiplying the power by time:28 x 3 = 84 kWhTo calculate the total cost we multiply the cost per kWh by the number of kWhs:84 x 18 = 1512 pence