Each night, from 10pm till 6am the outside lamp of the Smith family is turned on. The low-energy lamp uses 9 watt. A kilo-watt-hour costs 0,20 dollar. How many dollars does the Smith family lose each year because of this lamp?
10pm till 6am = 8 hours that the lamp is turned on.
8 x 9 watts =72 watts consumed in 1 day.
72 / 1000 =0.072 Kilo-watt/hours consumed in 1 day.
0.072 x $0.20 =$0.0144 - cost of electricity for 1 day.
$0.0144 x 365 days =$5.26 cost of electricity for the Smith family in 1 year.
10pm till 6am = 8 hours that the lamp is turned on.
8 x 9 watts =72 watts consumed in 1 day.
72 / 1000 =0.072 Kilo-watt/hours consumed in 1 day.
0.072 x $0.20 =$0.0144 - cost of electricity for 1 day.
$0.0144 x 365 days =$5.26 cost of electricity for the Smith family in 1 year.
