Question 93785
Two cell phone companies are promoting cell phone plans. Company A offers a flat fee of $90.00 per month. Company B offers a different plan. It will cost $15.00 per month for service .10 per minute. You will need to compare the two plans to decide which plan is better for you.
:
Sketch both equations on the same x - y plane.
:
Co A plan: y = 90
Co B plan: y = 15 + .10x, where x is the number of minutes used
Graph these two equations:
{{{ graph( 300, 200, -100, 1000, -10, 100, 90, 15+.1x) }}}
;
You can also solve this to find out the range of when Plan B is cheaper
.10x + 15 < 90
.10x < 90 - 15
.10x < 75
x < 75/.1
x < 750 minutes, plan B is cheaper, greater it's more expensive
:
How would you know which plan is better if minutes used or more information is given?
It's obvious that you would have to know how many minutes will be used each month.