Question : Along a path, 100 conical pillars are constructed. Each pillar has base radius 7 cm and height 24 cm. Find
(i) Curved surface area of one pillar. [2 Marks]
(ii) Find the total cost of painting 100 pillars at the rate of Rs. 120 per cm².
Doubt by Question by Purvi
Doubt by Question by Purvi
Solution :
No. of Pillars = 100
radius (r) = 7 cm
height (h) = 24 cm
height (h) = 24 cm
Slant Height (l)
l=√(r²+h²)
l=√[(7)²+(24)²]
l=√[49+576]
l=√[625]
l=25 cm
l=√(r²+h²)
l=√[(7)²+(24)²]
l=√[49+576]
l=√[625]
l=25 cm
(i) CSA of one pillar
= πrl
= (22/7)×7×25
= 22×25
= 550 cm²
(ii) CSA of one pillar = 550 cm²
CSA of 100 Pillars
= 550 × 100
=55000 cm²
Cost of Painting 1 cm² = Rs. 120
Cost of Painting 55000 cm²
= 55000 ×120
= Rs 6600000
= πrl
= (22/7)×7×25
= 22×25
= 550 cm²
(ii) CSA of one pillar = 550 cm²
CSA of 100 Pillars
= 550 × 100
=55000 cm²
Cost of Painting 1 cm² = Rs. 120
Cost of Painting 55000 cm²
= 55000 ×120
= Rs 6600000