SOLUTION: a candy bar is to be made out of cardboard that measures 80cm by 120cm. equal sized will be cut out of each corner, and then the ends and sides will be folded up to form a rectangu

Question 990438: a candy bar is to be made out of cardboard that measures 80cm by 120cm. equal sized will be cut out of each corner, and then the ends and sides will be folded up to form a rectangular box. what size square be cut from each corner to obtain a maximum volume?
Answer by Boreal(15235) (Show Source): You can put this solution on YOUR website!
The volume of the rectangular box is (120-2x)(80-2x)*x cm^3
This is (9600-400x+4x^2)*x
V=4x^3-400x^2+9600x
Take the first derivative and set it equal to zero
12x^2-800x+9600=0
4(3x^2-200x+3200)=0
The vertex (minimizes x) is at x=200/6=33.3 cm must be cut (33 1/3 is exact)
The volume is 13.3*53.3*33.3 (units cm for each)

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