Question

The height of a cone is 21 cm and slant height is 28 cm. Find the Total surface area of cone
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Answer 1

Answer:

TSA≈2707.78cm²

Step-by-step explanation:

h=21 cm

l=28 cm

r=  √l²+h²

=>r=7√7

 Therefore,

T. S. A=πrl+πr2

so,

TSA of cone=πrl+πr2

                     =(22/7)×(7√7)×28+(22/7)×(7√7)²

                     =2707.78 cm²

hope this helps u :-)

Answer 2

Given , Height of a cone , h = 21 cm

Slant height of a cone , l = 28 cm

Now apply pythagoras theorem for finding radius of the base of cone.

⇒ l² = h² + r²

⇒ 28² = 21² + r²

⇒ r = √(28²-21²)

⇒ r = 18.52 cm

Now Total Surface Area of cone , TSA

= Curved Surface Area of cone + Base of cone

= πrl + πr²

= π(18.52)(28) + π(18.52)²

= 1628.28 + 1076.99

= 2705.27 cm²

So the Total Surface Area of cone is 2705.27 cm²