Question

a man uses a 900w electric iron to press his cloth for an average of 4 hours a week for 5 weeks . if the cost of electrical energy is 30 kobo per unit , calculate the cost of energy for pressing

Answer 1

The total amount of energy can be calculated as the product of the power and the time the iron worked.

So the energy will be $900\,\mathrm{W}\cdot 4\,\mathrm{h}\cdot5 = 18000\,\mathrm{W\cdot h} = 18\,\mathrm{kW h}$ .

Therefore, the cost will be $18\,\mathrm{kW h} \cdot 30\,\mathrm{k/kWh} = 540\,\mathrm{k}.$