Chapter 8 Rational Functions - 8.3 Graph General Rational Functions - 8.3 Exercises - Problem Solving - Page 571: 36a

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Let $r$ be the inner radius and $h$ be the height The volume of the concrete used is $\pi(r+1)^2h-\pi r^2h+2\pi r^2\\=2\pi r h+2\pi r^2+\pi h$ Set this equal to $100$ Obtain $2\pi r h+2\pi r^2+\pi h=100\\2\pi r h+\pi h=100-2\pi r^2\\h(2\pi r+\pi)=100-2\pi r^2\\h=\frac{100-2\pi r^2}{2\pi r +\pi}$