It is required to make a closed cylindrical tank of height 1 m and base diameter 140 cm from a metal sheet.
Question. It is required to make a closed cylindrical tank of height $1 \mathrm{~m}$ and base diameter $140 \mathrm{~cm}$ from a metal sheet. How many square meters of the sheet are required for the same? $\left[\right.$ Assume $\left.\pi=\frac{22}{7}\right]$

Solution:

Height (h) of cylindrical tank = 1 m

Base radius $(r)$ of cylindrical $\operatorname{tank}=\left(\frac{140}{2}\right) \mathrm{cm}=70 \mathrm{~cm}=0.7 \mathrm{~m}$

Area of sheet required $=$ Total surface area of tank $=2 \pi r(r+h)$

$=\left[2 \times \frac{22}{7} \times 0.7(0.7+1)\right] \mathrm{m}^{2}$

$=(4.4 \times 1.7) \mathrm{m}^{2}$

$=7.48 \mathrm{~m}^{2}$

Therefore, it will require $7.48 \mathrm{~m}^{2}$ area of sheet.
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