A square piece of tin has 12 inches on a side. An open box is formed by cutting out equal square pieces at the corners and bending upward the projecting portion which remain. Find the maximum volume that can be obtained.

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Answer:

Explanation:

Given a square Piece whose side is 12 inches

Now square pieces are cut from each corner to make it a open box

Suppose x is the length of square piece at each corner

then

base square has a length of [tex]12-2x[/tex]

Dimension of new box is [tex](12-2x)\times (12-2x)\times x[/tex]

Volume [tex]V=(12-2x)\times (12-2x)\times x[/tex]

[tex]V=\left ( 12-2x\right )^2\cdot x[/tex]

For maximum volume differentiate with respect to x we get

[tex]\Rightarrow\frac{\mathrm{d} V}{\mathrm{d} x}=2\times \left ( 12-2x\right )\times \left ( -2\right )\cdot x+\left ( 12-2x\right )^2=0[/tex]

we get x=6 and 4 but at x=6 volume becomes zero therefore x=4 is valid

[tex]V=\left ( 12-2\cdot 4\right )^2\cdot 4[/tex]

[tex]V=4^3[/tex]

[tex]V=64\ in.^3[/tex]