NCERT Solutions for Class 9 Maths Chapter 13

Important NCERT Questions

Surface Areas and Volumes

NCERT Books for Session 2022-2023

CBSE Board, UP Board and Other state Boards

EXERCISE 13.3

Page No:221

Questions No:8

# 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 √(1.04 )= 1.02)

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Radius of cone r = 40/2 = 20 cm = 0.2 m and height h = 1 m

Let the slant height = lm

We know that l² = r² + h²

⇒ l² = (0.2)² + 1² = 0.04 + 1 = 1.04

⇒ l = √1.04 = 1.02 m

Curved surface area of 50 cones = 50 × 6.4056 = 32.028 m²

Cost of painting at the rate of Rs 12 per m² = Rs 12 × 32.028 = 384.34 (approx.)

Hence, the cost of painting the curved surface of 50 cones is Rs 384.34.

Get here all the solutions of class 9 Maths Exercise 11.1 Question 8

https://www.tiwariacademy.com/ncert-solutions/class-9/maths/chapter-11/

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