"Question 7 A joker’s cap is in the form of right circular cone of base radius 7 cm and height 24 cm. Find the area of the sheet required to make 10 such caps.
Class 9 - Math - Surface Areas and Volumes Page 221"
Answers
Right circular cone:
If a right angled triangle is revolved about one of the two sides forming a right angle keeping the other side fixed in position then the solid so obtained by segments is called right circular cone.
Slant height:
The length of the line segment joining the vertex to any point on a circular edge of the base is called the slant height of the cone.
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Given:
Radius of the cone (r) = 7 cm
Height of the cone (h) = 24 cm
Let l be the slant height l = √h² +r²
l = √24² + 7²=
√576+49
l = √625
l = 25 m
Curved surface of a jokers cap = Curved surface of the cone= πrl
= (22/7 × 7 × 25)
= 550 cm²
The Sheet required to make 1 cap = 550cm²
The Sheet required to make 10 caps = 550 × 10 = 5500cm²
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