Question

A kilowatt hour means 1000 watts of electricity are being used continuously for 1 hr The electric utility company in Laura's town charges $50.05309 for each kilowatt hour used. Laura heats her house with three electric heaters that

each use 1500 watts.

1.How much does it cost to heat her house for 1 day?

2. How many hours would a 75 watt lightbulb have to stay on to result in $1 for electricity
charges?

Answer 1

1. $5.73 per day
2. 251.1 hours

Explanation:

Given

the cost of electricity is $0.05309 for each kilowatt hour used.

Find

1. The one-day cost to use three 1500-watt electric heater
2. The number of hours for a 75 W light bulb to use $1 of electricity

Solution

1. The cost is the product of the number of kW, the number of hours, and the cost per kWh:

(1.5 kW/heater)(3 heaters)(24 hours)($0.05309/kWh)

= (108 kWh)($0.05309/kWh)

= $5.73

It costs Laura $5.73 per day to heat her house.

__

2. We want to find the number of hours (H) to run a .075 kW bulb for a cost of $1.

$1 = (.075 kW)(H)($0.05309)

H = 1/(0.05309·0.075) = 1/0.00398175 ≈251.1 . . . hours

A 75 W bulb can run about 251.1 hours on $1 worth of electricity.

Answer 2

1. $225.238905

2. 16 minutes or 0.27 hours

Explanation:

1.

1000w costs $50.05309 hence 1 w will cost $0.05005309

Each electric heater consumers 1500 W so for three, the total heat consumption will be 1500w*3=4500 W

Cost for the three heaters will be 4500*$0.05005309=$225.238905

Therefore, in 1 day, Laura will spend $225.238905 on heating alone

2.

1 kwh costs $50.05309 hence for 0.075 kwh it will sots 0.075*$50.05309=$3.75398175 Therefore for $1 you will spend
`\frac {1}{3.75398175}=0.26638382032624426051085623951155‬ hours`

This is approximately 16 mins