calculation in 2005 prep book wrong?

[e2me2]

I have Mikes 2005 Electrician Exam Prep Book & Master/Contractor Simulated Exam On page 14 1.26 Cost of power I think there is a error thus giving the wrong answer. I don't know were to send this to him so I'll post it
on page 14 1.26 Cost of Power
Once you get to the .1728Kw used then you go to the cost per hr it shows taking the 8.6 cents per Kwh/1000 to get .086
when I do this I get .0086
then .0086x.1728=.001486
x24hrs=.035664x365=13.01736 or $13.00per yr answer B
how are the getting .086 to come up with $130 to get C

 

[bob]

Once you get to the .1728Kw used then you go to the cost per hr it shows taking the 8.6 cents per Kwh/1000 to get .086
when I do this I get .0086
then .0086x.1728=.001486
x24hrs=.035664x365=13.01736 or $13.00per yr answer B
how are the getting .086 to come up with $130 to get C

8.6 cents per kwh = 0.086 cents/kwh not 0.0086 cents. Using your numbers I get $130.

 

[e2me2]

Once you get to the .1728Kw used then you go to the cost per hr it shows taking the 8.6 cents per Kwh/1000 to get .086
when I do this I get .0086
then .0086x.1728=.001486
x24hrs=.035664x365=13.01736 or $13.00per yr answer B
how are the getting .086 to come up with $130 to get C

8.6 cents per kwh = 0.086 cents/kwh not 0.0086 cents. Using your numbers I get $130.

how does 8.6 cents per kwh become .086 when to get kwh you need to devide by 1000 and 8.6/1000=.0086

 

[electricman2]

Not sure how they did it but I came up with $130.18 this way.
.1728*24*365*$.086/KWH=$130.18. (8.6cents =$.086)

 

[e2me2]

ok a little more detail the question reads

what is the cost per year at 8.6 cents per kwh for the power loss of two #10awg circut conductors that have a total resistance od .30 ohms with a current flow of 24A

there formula
P=I squared X R
p=24x24x0.30
p=172.8W

cost at 8.6cents per kwh
172.8w/1000=0.1728
8.6cents/1000=.086 {here is my question 8.6/1000=.0086}
they continue with
.086X.1728kw=.01486per hr
.01486x24x356=130.1995 or 130.20 D

A 1.30
b 130
c 13.00
d 1300

I use the .0086 and continue with
.0086x.1728=.00148608 per hr
x24x365=13.0180608 or$ 13.00 C

 

[don_resqcapt19]

8.6cents/1000=.086 {here is my question 8.6/1000=.0086}

You are changing the 8.6 cents to dollars in this part of the calculation. It should be 8.6cents/100=$0.086. The devide by 1000 is wrong.
Don

 

[e2me2]

8.6cents/1000=.086 {here is my question 8.6/1000=.0086}

You are changing the 8.6 cents to dollars in this part of the calculation. It should be 8.6cents/100=$0.086. The devide by 1000 is wrong.
Don

this makes sence now that i look at it
So anyway the book does have a error as it says 8.6/1000
this is what through me off. All I i could think of is 1000 was the kilo and devide that
ty Mike Holt needs to fix this in the book. Were do i let him know ? I dont see a spot for this

 

[charlie b]

So anyway the book does have a error as it says 8.6/1000

That is not an error. It is merely incomplete in its description. Here is what I mean:

8.6cents/1000=.086 {here is my question 8.6/1000=.0086}

What that is intended to say (in a mathematical expression) I will say (in an English sentence):

• The cost of "eight and six tenths of a cent for every one thousand watt-hours" is the same as "eighty six one-thousandths of a dollar for every one thousand watt-hours."

In other words, Mike's line could be clarified as follows:

8.6cents/1000 watt-hours = .086 dollars/1000 watt-hours

If you complete the solution of the question from that point, you will get the answer of $130.

Mike Holt needs to fix this in the book. Were do I let him know ? I don't see a spot for this

You can always send him an email. He gets many many emails every day, so don't expect a rapid reply. I think you can get his email address from his home page. We don't like to publish email addresses on this Forum. So if you need Mike's email address, send me a PM< and I'll send his address in a PM reply.