**A 2 kW heater, a 200 W TV and three 100 W lamps are all switched on from 6 p.m. to 10 p.m. What is the total cost at Rs. 5.50 per kWh?**

###### Answers:

For heater:

P = 2kW, t = 4h

E = P x t = 2 x 4 = 8kWh

For TV:

P = 200W = 0.2kW, t = 4h

E = P x t = 0.2 x 4 = 0.8 kWh

Lamps:

P = 100W = 0.1 kW, t= 4h, n= 3

E = n x P x t = 3 x 0.1 x 4 = 1.2 kWh

Total energy consumed = 8 + 0.8 + 1.2 = 10 kWh

Cost of 1 kWh = Rs. 5.50

Cost of 10 kWh = Rs. 5.50 x 10 = Rs. 55