Question

At Noise Pollution Cellular, plan A is $30.00 per month and $5.00 for every gigabyte of data. Plan B is $50.00 per month and $2.00 for every gigabyte of data used. Irfan wants to find out which plan is the best choice for him. On average, he uses five to eight GB of data per month. Write an equation for each plan with monthly data, , and total cost, .

Answer 1

A function for Plan A would be a(x) = 30 + 5x; a function for Plan B would be b(x) = 50 + 2x; if he uses 6 GB or less of data he is better off with Plan A; if he uses more than 6 GB of data he is better off with Plan B.

The one month cost for each plan is where we begin each function.  We then add the price per GB multiplied by the unknown number of GB, x.  This is where both functions come from.

Using 5 or 6 as x, we see that the cost for Plan A is less.  Using 7 or 8 for x, we see that the cost for Plan B is less.