An electric refrigerator rated 400 W is used for 8 hours a day. An electric iron box rated 750 W is used for 2 hours a day. Calculate the cost of using these appliances for 30 days, if the cost of I kWh is Rs 3/-.

Explanation

Given, For refrigerator, Power = P = 400 W, time = t = 8 hrs
Electrical energy consumed = `E_(1)=Pt=((400xx8))/1000=3.2kWh`
For iron box, P = 750 W. t = 2 hrs
`E_(2)=((750xx2))/1000=1.5kWh`
Total energy consumed by refrigerator and iron box in one day = `E_(1)+E_(2)=3.2+1.5=4.7`kWh.
Energy used in 30 days = `4.7xx30=141`kWh
Cost of 141 kWh = `141xx3=423`
The cost of using the appliances for 30 days is Rs. 423.