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

The total energy consumed by the refrigerator in 30 days
`=400 times 8 times 30=96000 Wh=96kWh`
The total energy consumed by the iron box in 30 days
`=750 times 2 times 30 =45000Wh=45kWh`
The total energy consumed by the refrigerator and iron box is
`=96kWh+45kWh=141kWh`
The sum of bill amount for 141 kWh at rate of Rs. 3 per 1 kWh is
`=141 times 3`
= Rs. 423