Word prob: mean cost per dir. c of printing x directories

[Violagirl]

I'm not really sure how to set these problems up into equations.

1) A service club wants to publish a directory of its members. Some investigation shows that the cost of typesetting and photography will be $921 and the cost of printing each directory will be $1.31. Find a function that gives the mean cost per directory, c, of printing x directories.

2) An electric company charges $9.55 per month plus 9 cents for each killowatt hour (kwh) of electricity used. Find a function that gives the mean cost per kwh, c, when using n kwh.

 

[pka]

Re: Word problems

You must show us some effort on your part!
What have you tried?
We are not here to do your work for you.

 

[Violagirl]

Re: Word problems

For the first problem, I believe I had to muliply x into 1.31 and then since $921 is an added cost, I set up the equation like this: 1.31x+921. But since I have to find the mean, does that mean I have divide something?

For the second one, I set it up in a similar way: .09n+9.55.

 

[this guy]

Re: Word problems

the "mean" normally means the average.

 

[Violagirl]

Re: Word problems

I see! I'm just not sure what I'm doing wrong in these problems.

 

[Violagirl]

Re: Word problems

You know, I think I just figured out. The way I have them set up would be the numerator and then I'd have the variable as the denominator, making me get the average cost!

 

[Deleted member 4993]

Re: Word problems

I'm not really sure how to set these problems up into equations.

1) A service club wants to publish a directory of its members. Some investigation shows that the cost of typesetting and photography will be $921 and the cost of printing each directory will be $1.31. Find a function that gives the mean cost per directory, c, of printing x directories.

\(\displaystyle Average \, cost/directory \, = \, 1.31 + \frac{921}{x}\)

2) An electric company charges $9.55 per month plus 9 cents for each killowatt hour (kwh) of electricity used. Find a function that gives the mean cost per kwh, c, when using n kwh.
similarly
\(\displaystyle Average \, cost/kwh \, = \, 0.09 + \frac{9.55}{n}\)

 

[Violagirl]

Thanks!