Posted by Nathan on .
The top and bottom margins of a poster are 2 cm and the side margins are each 4 cm. If the area of printed material on the poster is fixed at 386 square centimeters, find the dimensions of the poster with the smallest area.

Calculus 
Steve,
If the printed area has width x and height y,
xy = 386
The total area is thus
a = (x+8)(y+4) = (x+8)(386/x + 4)
= 4x + 418 + 3088/x
max area is where da/dx=0
da/dx = 4  3088/x^2
so, da/dx = 0 when x = 2√193
Now just evaluate y.