Question 15

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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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