# Math Help - Find the cost

1. ## Find the cost

A local photocopying store advertises as follows. " We charge 11 cents per copy for 350 copies or less, 7 cents per copy for each copy over 350 but less than 400 , and 4 cents per copy for each copy 400 and above. " Let x be the number of copies ordered and C(x) be the cost of the job (in cents ).
If x≤350, the cost of the copies is C(x)=_______________ cents
If 350<x<400, the cost of the copies is C(x)=________________ cents
If x≥400, the cost of the copies is C(x)=________________ cents

2. ## Re: Find the cost

Hello, spyder12!

You may be able to talk your way through this problem.
(There's one "border" where the reasoning is tricky.)

A local photocopying store advertises as follows.
. . "We charge 11 cents per copy for 350 copies or less,
. . 7 cents per copy for each copy over 350 but less than 400,
. . and 4 cents per copy for each copy 400 and above."

Let $x$ be the number of copies ordered and $C(x)$ be the cost of the job (in cents ).

If x ≤ 350, the cost of the copies is C(x) = ____ cents

If 350 < x < 400, the cost of the copies is C(x) = ____ cents

If x ≥ 400, the cost of the copies is C(x) = ____ cents

$\text{If }x \le 350,\text{ the cost is }\boxed{11x\text{ cents.}}$

$\text{If }351 \le x \le 399,\text{ we pay }250 \times 11 \,=\,3850\text{ cents for the first 350 copies.}$
$\text{Then we pay 7 cents for each copy over 350: }x-350$
$\text{The cost is: }\,3850 + 7(x-350) \:=\:\boxed{1400 + 7x\text{ cents.}}$

$\text{If }x \ge 400,\text{we pay 3850 for the first 350 copies,}$
$\text{Then we pay 7 cents each for the next }{\color{blue}49}\text{ copies: }343.$
$\text{Then we pay 4 cents for each copy over 399: }4(x-399)$
$\text{The cost: }\:3850 + 343 + 4(x-399) \:=\:\boxed{2597 + 4x\text{ cents.}}$

3. ## Re: Find the cost

I don't get the second part of the question. Please explain why you would pay 250 X 11