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All edges of a square pyramid are 18 centimetres. What is its volume? |
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Answer» Length of base edge a = 18 cm Volume = \(\frac{1}{3}a^2h\) Slant height, \(l=\sqrt{18^2-9^2}\) = \(\sqrt{324-81}\) = \(\sqrt{243}\) = \(9\sqrt{3}\) \(h=\sqrt{l^2-(a/2)^2}\) = \(\sqrt{243-81}\) = \(\sqrt{162}\) = \(9\sqrt{2}\) Volume = \(\frac{1}{3}a^2h\) = \(\frac{1}{3}\) x 182 x \(9\sqrt{2}\) = 1371.61 cm3 |
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