An oil funnel made of tin sheet consists of a10 cm long cylindrical portion attached to a frustum of a cone. If the total height is 22 cm, diameter of the cylindrical portion is 8 cm and the diameter of the top of the funnel is 18 cm, find the area of the tin sheet required to make the funnel (see Fig. 13.25)
Given:
Radius (r1) of upper circular end of frustum part = 
= 9 cm
Radius (r2) of lower circular end of frustum part = Radius of circular end of cylindricalpart = 
= 4 cm
Height (h1) of frustum part = 22 - 10 = 12 cm
Height (h2) of cylindrical part = 10 cm
Slant height (l) of frustum part
= 
= 13 cm
Area of tin sheet required = CSA of frustum part + CSA of cylindrical part
= π (r1 + r2) * l + 2πr2h2
= 
(9 + 4) * 13 + 2 * 
* 4 * 10
= 
[169 + 80]
= 
= 782 
cm2