"Question 2 Find the total surface area of a cone, if its slant height is 21 m and diameter of its base is 24 m.
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.
----------------------------------------------------------------------------------------------------
Given:
Diameter= 24m, (r) = 24/2 m = 12 m
Slant height (l) = 21 m
Total surface area of the cone = πr (l + r)
= 22/7 × 12 × (21 + 12)
= (22/7 × 12 × 33)
= 8712/7
= 1244.57 m²
Hence, the total surface area of a cone is 1244.57m²
========================================================
Hope this will help you....
here is ye answer !
========================================================================
Given us that,
Slant height ( l ) = 21 meter.
Diameter = 24 meter
we know that
r = diameter/2
=> r = 24/2 meter
=> r = 12 meter
.°. r = 12 meter.
.°. Total surface area of the cone = πr ( l + r )
= 22/7 × 12 × ( 21 + 12 )
= 22/7 × 12 × 33
= 8712/7
= 1244× 4/7 meter²
answer is 1244 × 4/7
hopes I helped
thanks
========================================================================