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A Bus Stop is Barricated from the Remaining Part of the Road, by Using 50 Hollow Cones Made Of Recycled Card-board. Each Cone Has a Base Diameter of 40 Cm and Height 1 M. If the Outer Side of Each - CBSE Class 9 - Mathematics

ConceptSurface Area of a Right Circular Cone

Question

A bus stop is barricated from the remaining part of the road, by using 50 hollow cones made of recycled card-board. 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 √1.04 = 1.02)

Solution

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

Height of cone=1m

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

=sqrt(1^2+(0.2)^2m)

=sqrt(1.04m=1.02m)

Curved surface area of each one

=pirl=(3.14xx0.2xx1.02)m^2

= 0.64056m^2

CSA of 50 such cone=50xx0.64056m^2=32.028m^2

Cost of painting 1m^2 area=Rs.12.

Cost of painting 32.028m^2 area=Rs(32.028xx12)

= Rs.384.326PS

Thus, it will cost Rs. 38434 (Approx) in painting the so hollow cones.

Is there an error in this question or solution?

APPEARS IN

RD Sharma Solution for Mathematics for Class 9 by R D Sharma (2018-19 Session) (2018 to Current)
Chapter 20: Surface Areas and Volume of A Right Circular Cone
Ex.20.10 | Q: 20 | Page no. 8
Solution A Bus Stop is Barricated from the Remaining Part of the Road, by Using 50 Hollow Cones Made Of Recycled Card-board. Each Cone Has a Base Diameter of 40 Cm and Height 1 M. If the Outer Side of Each Concept: Surface Area of a Right Circular Cone.
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