A consumer operates four 100 W incandescent lamps for 5.0 hours daily over a 30-day billing month. If electrical energy costs ₦50 per kilowatt-hour (kWh), calculate the total monthly electricity cost for these lamps.
Answer and explanation
Correct answer: C. ₦3,000
- Step 1: Calculate total power: 4 × 100 W = 400 W = 0.40 kW. Step 2. Total operating hours in 30 days: 5.0 h/day × 30 days = 150 hours. Step 3. Total electrical energy consumed: E = 0.40 kW × 150 h = 60 kWh. Step 4. Total cost: 60 kWh × ₦50/kWh = ₦3,000. Answer: ₦3,000. Why not the others: ₦2,400 assumes 4 hours per day; ₦3,600 uses 6 hours per day; ₦1,500 calculates for two lamps only.
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