Question

an electric refrigirator rated 400w operastes 8 hr /day.wt is the cost of energy to operate it for 30 days at rs.3.00 per kwh

Answer 1

hello friend!!

here's ur solution :-
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the total energy consumed by the refrigerator in 30 days would be
           400W* 8.0 hr/day*30days = 96000 W h
                                                      = 96 kW h

thus the cost of energy to operate the refrigirator for 30 days is 
                        
                              96 kW h * Rs.3.00 per kWh =Rs 288.00
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Hope it helps ya buddy !! :-)

Answer 2

Hi !

power = 400 W
time = 8hr
energy consumed in 1 day = power × time
                                          = 400 × 8
                                          = 3200 Wh
                                          = 3.2 kWh

Energy consumed in 30 days = 3.2 × 30 = 96 kWh
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Rate = Rs 3 / kWh

Total cost = 3 × 96 = Rs 288