waecmaths question:
The dimensions of a rectangular tanks are 2m by 7m by 11m. If its volume is equal to that of a cylindrical tanks of height 4cm. Calculate the base radius of the cylindrical tank [Take $\pi =\tfrac{22}{7}$]
Option A:
14m
Option B:
7m
Option C:
3½m
Option D:
1 ¾m
waecmaths solution:
$\begin{align} & Volume of rectangle=lbh=2\times 7\times 11=154{{m}^{3}} \\ & volume of cylinder=\pi {{r}^{2}}h=\frac{22}{7}\times {{r}^{2}}\times 4=\frac{88{{r}^{2}}}{7} \\ & \therefore \frac{88{{r}^{2}}}{7}=154{{m}^{3}} \\ & {{r}^{2}}=\frac{154\times 7}{88}=\frac{7\times 7}{4} \\ & r=\frac{7}{2}=3\tfrac{1}{2}m \\\end{align}$
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