The cost of running five 60 W lamps and four 100 W lamps for 20…

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

  • A.
    280.00
  • B.
    160.00
  • C.
    120.00
  • D.
    140.00
Correct Answer: Option D
Explanation

Total power in watt = 60*5 + 4*100
= 300 + 400
= 700w
Total power in kilo watt = 700/1000
= 0.7 killo w
Unit of electricity in killo watt-hour
= 0.7 * 20hrs
= 14 okwh
i.e If I kwh costs # 10.00
14kwh = 10.00 * 14 = #140

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