A bus stop is barricaded from the remaining part of the road, by using 50 hollow cones made of recycled cardboard. Each cone has a base diameter of 40 cm and height 1 m. - Mathematics

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A bus stop is barricaded from the remaining part of the road, by using 50 hollow cones made of recycled cardboard. Each cone has a base diameter of 40 cm and height 1 m. If the outer side of each of the cones is to be painted and the cost of painting is Rs 12 per m2, what will be the cost of painting all these cones?

`("Use "π = 3.14" and take "sqrt1.04= 1.02)`

 

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Solution

Radius (r) of cone = 40/2 = 20cm = 0.2m

Height (h) of cone = 1 m

Slant height (l) of cone`= sqrt(h^2+r^2)`

`=[sqrt((1)^2+(0.2)^2)]m=sqrt1.04m=1.02m`

CSA of each cone = πrl

= (3.14 × 0.2 × 1.02) m2 = 0.64056 m2

CSA of 50 such cones = (50 × 0.64056) m2

= 32.028 m2

Cost of painting 1 m2 area = Rs 12

Cost of painting 32.028 m2 area = Rs (32.028 × 12)

= Rs 384.336

= Rs 384.34 (approximately)

Therefore, it will cost Rs 384.34 in painting 50 such hollow cones.

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Chapter 13: Surface Area and Volumes - Exercise 13.3 [Page 221]

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NCERT Mathematics Class 9
Chapter 13 Surface Area and Volumes
Exercise 13.3 | Q 8 | Page 221

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