What is the cost of running seven 40 W lamps and five 80 W lamps…

What is the cost of running seven 40 W lamps and five 80 W lamps for 12 hours of the electrical energy cost N7.00kWh?

  • A.
    N80.00
  • B.
    N45.36
  • C.
    N65.00
  • D.
    N57.12
Correct Answer: Option D
Explanation

Seven 40W lamps = 7 × 40 = 280W
Five 80W lamps = 5 × 80 = 400W
Total power = 280W + 400W
= 680W
= (frac{680KW}{1000}) = 0.68KW
The kilowatt hour = 0.68 KW × 12 hrs
= 8.16 KWh
Cost is N 7 per KWh
So the cost of running them = 8.16KWh × N 7/KWh
= 57.12

There is an explanation video available below.

You May Also Like