How Do You Calculate the Cost of Running a Steam Iron?

[peaceandlove]

Homework Statement

A steam iron draws 5.3 A from a 114 V line. (a) How much internal energy is produced in 76 minutes? Answer in J. (b) How much does it cost at $0.75/kW*hr to run the steam iron for 76 minutes? Answer in units of cents.

Homework Equations

1) U = VIt

The Attempt at a Solution

Using equation 1, I found the internal energy produced to be 2755152 J. However, I'm having a problem with figuring out part (b). I know I'm supposed to convert J to kW*hr in order to figure out the cost and that 1 watt = 1 J/s. Using that information I divided the internal energy by the time, 4560 seconds, giving me 604.2 watts or 0.6042 kW. I then times that by the cost per kW/hr and the amount of time in hours. I got 0.57399, but for some reason it's not the right answer.

 

[rock.freak667]

2755152 J =2755152 Ws

Divide by 1000 to get it in kWs, then divide by 3600s to get it in kW*hr

 

[LowlyPion]

Answer in units of cents.
... I got 0.57399, but for some reason it's not the right answer.

Maybe enter it in cents?

 

[peaceandlove]

2755152 J =2755152 Ws

Divide by 1000 to get it in kWs, then divide by 3600s to get it in kW*hr

I tried that and I get the same exact answer that I got. I even tried putting it in as 0.57 but that was marked wrong as well...

 

[rock.freak667]

I tried that and I get the same exact answer that I got. I even tried putting it in as 0.57 but that was marked wrong as well...

Your answer is $0.57399, convert that into cents.