Question

15 bulbs of 60 volt each run on 6 hours daily and a refrigerator of 300 watt runs for 5 hours daily workout for day bill at 3 rupees per unit

Answer 1

Hi.

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Power of 1 bulb = 60 W

Power of 15 bulbs = 15*60 = 900 W or 900/1000 = 9/10 kW

Time = 6 hrs

Energy = P*T = 9*6/10 = 54/10 = 5.4 units

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Power of Refrigerator = 300 W = 300/1000 = 3/10 kW

Time = 5 hrs

Energy = 3*5/10 = 15/10 = 1.5 units

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Total energy per day = 6.9 units

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Cost per day per unit = Rs. 3

Thus, total cost = Rs. 3 * 6.9 = Rs. 20.7

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Hope it helps.