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# Twenty One 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 - Mathematics

Answer in Brief

Twenty one 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?

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#### Solution

$\text{ Given } :$
$\text{ Diameter of the pillars = 0 . 5 m}$
$\text{ Radius of the pillars, r = 0 . 25 m }$
$\text{ Height of the pillars, h = 4 m }$
$\text{ Number of pillars } = 21$
$\text{ Rate of cleaning = Rs 2 . 50 per square metre }$
$\text{ Curved surface area of one pillar } = 2\pi rh$
$= 2 \times \frac{22}{7} \times 0 . 25 \times 4$
$= 2 \times \frac{22}{7}$
$= \frac{44}{7} m^2$
$\therefore \text{ Curved surface area of one pillar } = \frac{44}{7} \text{ m} ^2$
$\text{ Cost of cleaning 21 pillars at the rate of Rs 2 . 50 per m}^2 = \text{ Rs } 2 . 5 \times 21 \times \frac{44}{7}$
$= 7 . 5 \times 44$
$\therefore \text{ Cost of cleaning 21 pillars at the rate of Rs 2 . 50 per m} ^2 = Rs 330$

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#### APPEARS IN

RD Sharma Class 8 Maths
Chapter 22 Mensuration - III (Surface Area and Volume of a Right Circular Cylinder)
Exercise 22.1 | Q 15 | Page 11
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