Question

Find the t.s.a of cone whose diameter of base is 8cm and height is 3cm

Answer 1

HERE,
diameter of cone = 8 cm
: . radius of base =r = diameter / 2
= 8 / 2 = 4 cm
height of cone = h= 3cm

TO FIND = Total surface area of cone = ?

TO SOLVE =
slant height ^2 = height ^2 + radius ^2
l^2 = h^2 + r^2
l^2 = 3^2 + 4^2
l^2 = 9 + 16
l^2 = 25
: . by taking square root
l = underoot 25
l = 5 cm

T.S.A of cone = \pi × r (r + l)
= 3.14 × 4 ( 4 + 5 )
= 3.14 × 4 × 9
= 113.04 cm^2

: . T.S.A of cone = 113.04 cm^2