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Volume, SM-Bank 159

A right cylinder has a volume of \(11\ 451\) cubic metres. Calculate the radius of the cylinder if the height is 45 metres.

Give your answer to the nearest whole centimetre.  (2 marks)

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\(9\ \text{m}\)

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\(V\) \(=\pi r^2h\)
\(11\ 451\) \(=\pi\times r^2\times 45\)
\(11\ 451\) \(=10\pi\times r^2\)
\(r^2\) \(=\dfrac{11\ 451}{45\pi}\)
\(r^2\) \(=80.999\dots\)
\(r\) \(=\sqrt{80.999}=8.999\dots\)
\(r\) \(\approx 9\ \text{m (nearest whole m)}\)

 
\(\therefore\ \text{The radius of the cylinder is approximately 9 m}\)