Hello OneidaFL Originally Posted by

**OneidaFL** A cellular phone company offers a contract for which C, in dollars of t minutes of telephone is given by

C= 0.25(t-400) + 48.95

Assuming that t > 400

What times will keep (for the cost) between $90.70 and $129.95

Phone time must be between ________ Min and _______ Min.

What do I have to do first? Estimate the amount of minutes?

You need to solve two equations for $\displaystyle \displaystyle t$, to find the values of $\displaystyle \displaystyle t$ that make $\displaystyle C = 90.70$ and $\displaystyle C = 129.95$.

That is, you need to solve:

$\displaystyle 90.70 =0.25(t-400) + 48.95

$

and

$\displaystyle 129.95 =0.25(t-400) + 48.95

$

These solutions will give you the minimum and maximum values you require.

Can you complete it now?

Grandad