Question

A page should have perimeter of 42 inches. The printing area within the page

Answer 1

Overall  dimensions of the page in order to maximize the printing area is  page should be 11 inches wide and 10 inches long .

Step-by-step explanation:

We have , A page should have perimeter of 42 inches. The printing area within the page  would be determined by top and bottom margins of 1 inch from each side, and the  left and right margins of 1.5 inches from each side. let's assume  width of the page be x inches  and its length be y inches So,

Perimeter = 42 inches

⇒ $2(x+y) = 42\\x+y = 21\\y = 21-x$

width of printed area = x-3  & length of printed area = y-2:

area = $length(width)$

$area = (x-3)(y-2)\\area = (x-3)(21-x-2)\\area = (x-3)(19-x)\\area = -x^{2} + 22x -57$

Let's find $\frac{d(area)}{dx}$:

$\frac{d(area)}{dx}$ = $\frac{d(-x^{2}+22x-57)}{dx} = -2x +22$ , for area to be maximum $\frac{d(area)}{dx}$= 0

⇒ $-2x+22 = 0\\2x =22\\x=11 inches$

And ,

$y = 21-x\\y = 21-11\\y = 10 inches$

∴ Overall  dimensions of the page in order to maximize the printing area is  page should be 11 inches wide and 10 inches long .