Posted by **Celina** on Tuesday, December 16, 2008 at 4:38pm.

Another question:

A cell phone company charges $60 for a cell phone and $40 per month under its economy plan. Formulate and graph a model that can be used to determine the total cost, C(t), of operating a cell phone for t months. Find the total cost for 5 and 1/2 months of service and the domain of C.

I understand everything except how you would find the domain of C. Please walk me through it so I can apply it to other problems. Thank you so much!

- Algebra -
**Reiny**, Tuesday, December 16, 2008 at 5:33pm
did you have C(t) = 40t + 60 ?

now the graph would only make physical sense for the part in the first quadrant.

the y-intercept is the point (0,60), (even with no calls you would pay $60)

the graph would continue to rise as t increases.

so the lowest Cost is 60 and there is really no upper limit, but we have to be reasonable about large values of t

e.g. if t = 1000, this would make no sense because 1000 months from now, cells phones may only be found in museums.

I would say the domain of t is any reasonable value of t , t > 0

you said "domain of C", what you meant is the range of C

domain deals with the horizontal variable,

range deals with the vertical variable of your function.

- Algebra -
**Celina**, Tuesday, December 16, 2008 at 7:23pm
That's funny, because in my packet, it said to "find the domain of C." But I see how that would not make sense.

Thanks!

## Answer This Question

## Related Questions

- Statistics - Professor does not teach from a book so am not sure how to apply ...
- Statistics - I have a take home test I am working on. Any help would be ...
- Gr10 Math - Charlene is looking into cell phone plans. Cell plus gives unlimited...
- algebra - Amy has set aside $150 a month for her cell phone bill. Thecost for a ...
- math - 73. Cell Phone Plan A cell phone plan costs $3.95 per month plus $0.07 ...
- pre-albegra word problem - I need to write a verbal rule to determine the total ...
- Math - One cell phone plan costs $15 per month plus $0.10 per minute used. A ...
- ALGEBRA HELP OR I AM GONNA FAIL I CANT DO THIS - compare two cell phone ...
- math - sally's cell phone company charges a flat rate of $15.00 per month and $...
- Math - A cell phone company charges a monthly fee of $17.95 and $0.03 per minute...

More Related Questions