SOLUTION: An open-topped box can be created by cutting congruent squares from each of the four corners of a piece of cardboard that has dimensions of 20cm by 30cm and folding up the sides. D

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Question 1060643: An open-topped box can be created by cutting congruent squares from each of the four corners of a piece of cardboard that has dimensions of 20cm by 30cm and folding up the sides. Determine the dimensions of the squares that must be cut to create a box with a volume of 1008cm^3.
Found 2 solutions by josgarithmetic, ikleyn:
Answer by josgarithmetic(39616) About Me  (Show Source):
You can put this solution on YOUR website!
Dimensions x and y
Uniform sidelength of each square, w
Volume of box, v

w is also how high or tall the box.
Bottom area when flaps folded will be %28x-2w%29%28y-2w%29

MAIN STARTING EQUATION: w%28x-2w%29%28y-2w%29=v

STEPS
w%28xy-2yw-2xw%2B4w%5E2%29-v=0
xyw-2yw%5E2-2xw%5E2%2B4w%5E3-v=0
4w%5E3-2%28x%2By%29w%5E2%2Bxyw-v=0-------Cubic equation in the unknown variable, w.

Make the substitutions and simplify from system%28x=20%2Cy=30%2Cv=1008%29 and the equation becomes w%5E3-25w%5E2%2B150w-252=0.

You can try looking for zeros or roots based on Rational Roots theorem. The practical factorizations which would be useful for the term, -252 would be 252=2%2A126=3%2A84=4%2A63=6%2A42; so continue this by testing roots 1, 2, 3, 4, 6, 7, and see if any give remainder of 0 when using synthetic division.


(3 and 4.92 both will work).

Answer by ikleyn(52776) About Me  (Show Source):
You can put this solution on YOUR website!
.
An open-topped box can be created by cutting congruent squares from each of the four corners of a piece of cardboard
that has dimensions of 20 cm by 30 cm and folding up the sides. Determine the dimensions of the squares that must be cut
to create a box with a volume of 1008cm^3.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

(20-2x)*(30-2x)*x = 1008.

%28600+-+60x+-+40x+%2B+4x%5E2%29%2Ax = 1008,

%284x%5E2+-+100x+%2B+600%29%2Ax = 1008,

%28x%5E2+-+25x+%2B+150%29%2Ax = 252,

x%5E3+-+25x%5E2+%2B+150x+-+252 = 0,


One root is x= 3.


So, one solution is x= 3.


Two others are  x= 11-sqrt%2837%29 =~ 4.92  and  x= 11%2Bsqrt%2837%29 =~ 17.08. The latest is TOOOOO big.


Check.  (20-2*3)*(30-2*3)*3 = 14*24*3 = 1008.


Answer.  One solution is x= 3.  Another is  x= 11-sqrt%2837%29 =~ 4.92





Plot y = x%5E3+-+25x%5E2+%2B+150x+-+252