Answer:
30. $3.85
31. $2.22
Step-by-step explanation:
30. The time duration of the kitchen clock is left on = All day = 24 hours
The power rating of the kitchen clock, P = 4 watts
The electricity cost in Alberta, R = $0.11 per kilowatt hour
The total number of hours the kitchen clock is on during the year, 't', is given as follows;
t = Number of hours per day × Number of days per year
∴ t = 24 hours/day × 365 days/year = 8,760 hours
The energy consumption of the kitchen clock, per year, E = P × t
∴ E = 4 watts × 8,760 hours = 35,040 watts-hour = 35.040 kw·h
The cost of operating the clock in one year, C = E × R
∴ Operating cost for the kitchen clock
∴ C = 35.040 kw·h × $0.11/(kw·h) = $3.8544 ≈ $3.85
The cost of operating the clock in one year, C ≈ $3.85
31. The power rating of the ghetto blaster, P = 28 watts
The time duration the ghetto blaster was on during an average month = All day = 24 hours
The number of days during an average month, n = 30 days
The cost of electricity in Alberta, R = $0.11 per kilowatt hour
The time in hours the ghetto blaster was on, t = 30 days/month × 24 hours/day
∴ t = 720 hours per month
The cost of operating the ghetto blaster in one month, C = P × t × R
∴ C = 28 W × 720 hours × 1 kw·h/(1000 w·h)× $0.11/(kw·h) = $2.2176
∴ The cost of operating the ghetto blaster in one month, C ≈ $2.22