A. N80.00
B. N45.36
C. N65.00
D. N57.12
Correct Answer:
Option D – N57.12
Explanation
Seven 40W lamps = 7 × 40 = 280W
Five 80W lamps = 5 × 80 = 400W
Total power = 280W + 400W
= 680W
= 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
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![Five 80-W and three 100W are run for 8 hours. If the cost of energy is N5.00 per unit, calculate the cost of running the lamp. [1 unit = 1 kWh]](https://erudites.ng/wp-content/plugins/contextual-related-posts/default.png "Five 80-W and three 100W are run for 8 hours. If the cost of energy is N5.00 per unit, calculate the cost of running the lamp. [1 unit = 1 kWh]")
