Find the area of the iron sheet required to prepare a cone 20 cm high with base radius 21 cm.

Explanation

r = 21cm, h= 20cm
therefore `l= sqrt(r^2+h^2) = 29cm`
therefore Area of the sheet = total surface area of the cone
=`pi rl+ pi r^2 = pi r(l+r)`
=`(22)/7 xx 21[29+21]` = `3300 cm^2`