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# A Cylindrical Pillar Has a Radius of 21 Cm and a Height of 4 M. Find : (I) the Curved Surface Area of the Pillar (Ii) Cost of Polishing 36 Such Cylindrical Pillars at the Rate of ₹ 12 per M2. - Mathematics

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Sum

A cylindrical pillar has a radius of 21 cm and a height of 4 m. Find :
(i) the curved surface area of the pillar
(ii) cost of polishing 36 such cylindrical pillars at the rate of ₹ 12 per m2.

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#### Solution

Radius of the cylinder = 21 cm

= 21/100 = 2.1m

Height of the cylinder = 4 m

(i) Curved surface area of the cylinder = 2pirh

= 2 xx 22/7 xx 2.1 xx 4 = 52.8 m2

(ii) Cost of polishing 1 m2 = ₹ 12

Cost of polishing (36 xx 52.8 "m"^2)

= ₹ 12 xx 1900.80 = ₹ 22,809.60

Concept: Surface Area of a Cuboid
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#### APPEARS IN

Selina Concise Mathematics Class 8 ICSE
Chapter 21 Surface Area, Volume and Capacity
Exercise 21 (D) | Q 9 | Page 243
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