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You are asked to build an open cylindrical can (i.e. no top) that will hold $665.5$ cubic inches. To do this, you will cut its bottom from a square of metal and form its curved side by bending a rectangular sheet of metal.

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(a) Express the total amount of material required for the square and the rectangle in terms of $r$.

I just need a hind nothing more, do I have to add the area of the rectangle with the area of the square?

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"do I have to add the Area of the rectangle with the area of the square?" => Yes. – Juanito Jul 3 '14 at 3:01
Hint: $\pi r^2 h=665.5$. – André Nicolas Jul 3 '14 at 3:02
@AndréNicolas So the Area of the rectangle will be 1331/r. What about the square, why there is a circle in it? – John Jul 3 '14 at 3:14
The square has area $4r^2$. – André Nicolas Jul 3 '14 at 3:18
In spite of the opinion of physicists, it is not necessarily useful to worry about units here. But if you really want units, the derivatives' unit is the inch. – André Nicolas Jul 3 '14 at 3:24

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