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The cost of running five 60 W lamps and four 100 W lamps for 20 hours if electri...


Question

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

Options

A) 280.00

B) 160.00

C) 120.00

D) 140.00


The correct answer is D.

Explanation:

Total power in watt = 60*5 + 4*100
= 300 + 400
= 700w
Total power in kilo watt = 700/100
= 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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Dicussion (1)

  • Total power in watt = 60*5 + 4*100
    = 300 + 400
    = 700w
    Total power in kilo watt = 700/100
    = 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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