Question

A cylinder has a volume of 315pi cubic meters and a height of 21 meters. What is the area of the base?

Answer 1

its B=36

Explanation:

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Answer 2

`\bf \textit{volume of a cylinder}\\\\ V=\pi r^2 h\qquad \begin{cases} r=radius\\ h=height\\ -----\\ V=315\pi \\ h=21 \end{cases}\implies 315\pi =\pi r^2(21) \\\\\\ \cfrac{315\pi }{21\pi }=r^2\implies 15=r^2\implies \boxed{√(15)=r}\\\\ -------------------------------\\\\ \textit{since the area of the base of the cylinder is a circle with radius \underline{r}} \\\\\\ \textit{area of a circle}\\\\ A=\pi r^2\qquad A=\pi \left( \boxed{√(15)} \right)^2\implies A=15\pi`