Final answer:
The power of the toaster oven is 1,500 watts. To toast a piece of bread with a 1200-W toaster for 1 minute uses 72,000 J or 0.02 kWh of energy, which costs 0.18 cents at a rate of 9.0 cents per kWh.
Step-by-step explanation:
To calculate the power of the toaster oven given that it uses 67,500 joules of energy in 45 seconds, you can use the formula P = W/t, where P is power in watts (W), W is the work done or energy used in joules (J), and t is the time in seconds (s). In this case, the power is calculated as P = 67,500 J / 45 s, which equals 1,500 watts or 1.5 kilowatts (kW).
For the question involving a 1200-W toaster and cooking time of 1 minute (which is equivalent to 60 seconds), the electrical energy needed can be calculated using the same formula for power. So we have E = P x t = 1200 W x 60 s = 72,000 J or 0.02 kWh (remembering that 1 kWh = 3.6 x 106 J). To find the cost, multiply the electrical energy in kWh by the cost per kWh. Therefore, the cost = 0.02 kWh x 9.0 cents/kWh = 0.18 cents per slice of toast.