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Question
A family uses a light bulb of 100W, a fan of 100W, and a heater of 1000W, each for 8 hours a day. If the cost of electricity is Rs. 2 per unit, what is the expenditure to the family per day, on electricity?
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Solution
Power consumed in watt-hours
= 100 × 8 + 100 × 8 + 1000 × 8
(bulb) (fan) (heater)
= (800 + 800 + 8000) watt-hours
= 9600 watt hour (units)
i.e. Electric energy comsumed in kWh (units)
`= 9600/1000 = 9.6` kWh.
Cost at Rs. 2 per unit or per kWh
= Rs. 2 × 9.6 = Rs. 19.20.
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