Question

an electric refrigerator rated 400 watt is used for 8 hours a day and electric iron box rated 750 watt is used for 2 hours a day calculate the cost of using these appliances for 30 days if the cost of one kilowatt hour is rupees 3​

Answer 1

total power used by refrigerator daily= 400×8 w.h= 3200 watt hour

Total power used by refrigerator in one month= 3200×30 watt hour=96000 watt hour= 96 kilowatt hour

In this way, total power used by electric iron in one month=

750×2×30=45000 watt hour= 45 kilowatt hour.

So, net power consumption in one month=( 96+45) kilowatt hour

= 141 kilowatt hour

So, net cost = (141×3) Rs

=423 Rs

Answer 2

Answer:

Given,

Power = P = 400W = 400/1000 kW = 0.4 kW

Total time for which the refrigerator operated = t = 8 hours x 30 days = 240 h

Since, Energy consumed = P x t E = 0.4 x 240 kWh = 96 kWh

Therefore, total cost required to operate the refrigerator for the month = 96 x 30 = 2880 INR.