Question

"Question 1 Diameter of the base of a cone is 10.5 cm and its slant height is 10 cm. Find its curved surface area.

Class 9 - Math - Surface Areas and Volumes Page 221"

Answer 1

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: Diameter= 10.5 cm

Radius (r) = 10.5/2 cm = 5.25 cm

Slant height (l) = 10 cm

Curved surface area of the cone = (πrl)

=(22/7 × 5.25 × 10)
=165 cm²

Hence, the curved surface area of a cone =165cm²

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Hope this will help you ..

 

 

 

Answer 2

Hi friend ✋

Here r =(10.5/2)cm
=5.25cm and l=10

Curved surface area if the cone=πrl cm square

=(22/7×5.25×10)cm square

=165 cm square..

Hope it helps ♌♌⛎⛎