An electric refrigerator rated 300 W is used for 8 hours a day. An electric iron box rated 750 Wis used for 2 hours a day. Calculate the cost of using these appliances for 30 days, if the cost of 1 kWh is Rs. 3/-

Explanation

The total energy consumed by the refrigcrator in 30 days
`=400xx8xx0= 96000 Wh - 96 kWh`
The total energy consumed by the iron box in 30 days `750xx2xx30 = 45000 Wh= 45 kWh`
The total energy consumed by the refrigerator and iron box is `96kWh +45kWh-141 kWh`
The surn of bill amount for 141 kWh at rate of Rs. 3 pcr 1 kWh is `-141 xx 3 = Rs. 423`