A house is fitted with 5 tubes each f 40 W. If all the tubes are lighted for 20 hours and if the cost of electrical unit is Rs. 0.50, the total cost of electricity consumed is:
The electrical power of a single tube in kilowatt= 
The electrical power of a 5 tubes in kilowatt=0.2kW
Total unit of power consumed = 0.2 × 20 = 4kWh = 4units
The cost of electricity consumed = 4 × 0.50 = Rs. 2
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