Ex 11.1, 7 - Chapter 11 Class 9 Surface Areas and Volumes

Last updated at April 16, 2024 by Teachoo

Transcript

Ex 11.1,7
A joker’s cap is in the form of a right circular cone of base radius 7 cm and height 24 cm. Find the area of the sheet required to make 10 such caps.
Sheet required will be on the Curved Surface Area
Curved Surface Area of 1 jokers cap = πrl
Given radius = r = 7 cm
Height = h = 24cm
Let slant height be l
We know that
l2 = h2 + r2
l2 = "(24)2 + (7)2"
l2 = 576+49
l2 = 625
l = √625
l = √("252" )
l = 25 cm
Curved Surface Area of 1 jokers cap = πrl
= 22/7 × 7 × 25 cm2
= 22 × 1 × 25 cm2
= 550 cm2
So,
Curved Surface Area of 1 jokers cap = 550 cm2
Curved Surface Area of 10 jokers cap = 10 × 550 cm2
= 5500 cm2

Davneet Singh has done his B.Tech from Indian Institute of Technology, Kanpur. He has been teaching from the past 14 years. He provides courses for Maths, Science, Social Science, Physics, Chemistry, Computer Science at Teachoo.

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