The cost of running five 60 W lamps and four 100 W lamps for 20 hours if electrical energy cost #10.00 per kwh is
- 280.00
- 160.00
- 120.00
-
140.00
The correct answer is: D
Explanation
Total power in watt = \(60\times5 + 4\times100\)
= 300 + 400
= 700W
Total power in kilo watt = 700/1000
= 0.7kW
Unit of electricity in kilowatt-hour
= 0.7 * 20hrs
= 14 okwh
i.e If I kwh costs # 10.00
14kwh = \(10.00 \times14\) = #140
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