waecmaths question:
The slant height of a cone is 5cm and the radius of its base is 3cm. Find, correct to the nearest whole numbers, the volume of the cone [Take $\pi =\tfrac{22}{7}$]
Option A:
48cm3
Option B:
47cm3
Option C:
38cm3
Option D:
13cm3
waecmaths solution:
$\begin{align} & height=\sqrt{{{5}^{2}}-{{3}^{2}}}=\sqrt{16}=4cm \\ & h=4cm \\ & V=\tfrac{1}{3}\pi {{r}^{2}}h \\ & V=\tfrac{1}{3}\times \tfrac{22}{7}\times {{3}^{2}}\times 4c{{m}^{3}} \\ & V=37.71c{{m}^{3}} \\ & V\approx 38c{{m}^{3}} \\\end{align}$
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