Answer: a) $1.6123 , b) $0.00588 c) $0.392
Explanation:
Note, all power in watts is converted to kilowatts and all units of time is converted to hours.
The cost of electricity is $0.12 for 1kwh.
Question a.
Power = 40w to kilowatts = 40/1000 = 0.04kw
Time = 2 weeks to hours = 24 * 14 = 336 h.
Energy = power * time.
Energy = 0.04 * 336 = 13.44kwh.
If 1kwh cost $0.12, then 13.44 kwh will cost
0.12 * 13.44 = $1.6132.
Question b
Power = 980w to kilowatts = 980/1000= 0.98kw
Time = 3 minutes to hours = 3/60 = 0.05 h
Energy = power * time
Energy = 0.98 * 0.05
Energy = 0.049kwh
If 1kwh cost $0.12, then 0.049 kwh will cost
0.049 * 0.12 = $0.00588
Question c
Power = 4900w to kilowatts = 4900/1000= 4.9kw.
Time = 40 minutes to hours = 40/ 60 = 0.67.
Energy = power * time
Energy = 4.9 * 0.67
Energy = 3.267 kwh
If 1 kwh cost $0.12, then 3.267kwh will cost
3.268 * 0.12 = $ 0.392
