Twenty cylindrical pillars of the Parliament House are to be cleaned. If the diameter of each pillar is $0.50\ m$ and height is $4\ m$. What will be the cost of cleaning them at the rate of $Rs.\ 2.50$ per square metre?


Given:

Twenty cylindrical pillars of the Parliament House are to be cleaned.

The diameter of each pillar is $0.50\ m$ and height is $4\ m$.

To do:

We have to find the cost of cleaning the pillars at the rate of $Rs.\ 2.50$ per square metre.

Solution:

Number of pillars $= 20$

Diameter of each pillar $= 0.50\ m$

This implies,

Radius $(r)=\frac{0.50}{2}$

$=0.25 \mathrm{~m}$

$=25 \mathrm{~cm}$

Height of each pillar $=4 \mathrm{~m}$

Therefore,

Curved surface area of each pillar $=2 \pi r h$

$=2 \times \frac{22}{7} \times \frac{25}{100} \times 4$

$=\frac{44}{7} \mathrm{~m}^{2}$

Total area of 20 pillars $=20\times\frac{44}{7}$

$=\frac{880}{7} \mathrm{~m}^{2}$

Rate of cleaning the pillars $=Rs.\ 2.50$ per $\mathrm{m}^{2}$

Total cost of cleaning $=Rs.\ 2.50 \times \frac{880}{7}$

$=Rs.\ \frac{250 \times 880}{100 \times 7}$

$=Rs.\ \frac{2200}{7}$

$=Rs.\ 7314.28$

Updated on: 10-Oct-2022

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