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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.
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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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