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Question
A consumer uses 4 lamps of 60 watt, 2 lamps of 40 watt, and 2 lamps of 100 watt. All these are used for 6 hour daily. Find the total bill for 30 days when the rate of energy is 75 paise per unit and the meter rent is Rs. 1.
Solution
Total power consumption of 4 lamps of 60 watt each = 60 × 4 = 240 W
Total power consumption of 2 lamps of 40 watt each = 40 × 2 = 80 W
Total power consumption of 2 lamps of 100 watt each = 100 × 2 = 200 W.
∴ Total power consumption = (240 + 80 + 200) = 520 W
∴ Total watt-hour for 6 hours a day for 30 days = 520 × 6 × 30 = 93600 watt-hour
Hence, kilowatt-hour =`93600/1000 = 93.6` kWh
Cost of electric energy at 75 p.per kWh =`(93.6 xx 75)/100 = 70.20`
∴ Total cost = Rs. 70.20 + Rs. 1.0 (Meter rent)
= Rs. 71.20
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