- 2068 Chaitra · 4 marks
Cost of electrical energy for appliances
Short answer
Energy: toaster 1.2kW×0.5h=0.6kWh, bulbs 0.3kW×4h=1.2kWh, washer 0.4kW×0.75h=0.3kWh, dryer 4.8kW×1/3h=1.6kWh. Total 3.70 kWh × Rs 7 = Rs 25.90.
What is the total cost of using the following at Rs 7 per kilowatt hour? i) A 1200 W toaster for 30 min ii) Six 50 W bulbs for 4 hours iii) A 400 W washing machine for 45 min. iv) A 4800 W electric clothes dryer for 20 min.
Energy (kWh) = power (kW) × time (h). Cost = energy × Rs 7.
| Appliance | Power | Time | Energy |
|---|---|---|---|
| Toaster | 1.2 kW | 0.5 h | 0.60 kWh |
| Six bulbs | 6 × 50 W = 0.3 kW | 4 h | 1.20 kWh |
| Washing machine | 0.4 kW | 0.75 h | 0.30 kWh |
| Clothes dryer | 4.8 kW | 1/3 h | 1.60 kWh |
Total energy = 0.60 + 1.20 + 0.30 + 1.60 = 3.70 kWh
Total cost = 3.70 × 7 = Rs 25.90
Item costs: toaster Rs 4.20, bulbs Rs 8.40, washing machine Rs 2.10, dryer Rs 11.20.
Answer: Total cost = Rs 25.90
✓ Answer checked by Claude Opus 5.5 (high effort)
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