Question

The power rating of a clock is 10 W, and the cost of electrical energy is $0.15 per kilowatt-hour.

Rounded to the nearest cent, how much does it cost to run the clock for one whole week?

$0.04
$0.25
$1.68
$11.20

Answer 1

10 W = 0.01 kW. One week = 7×24 = 168 hours, so energy = 0.01 kW × 168 h = 1.68 kWh.
Cost = 1.68 kWh × $0.15/kWh = $0.252 ≈ $0.25.

Answer: $0.25