From a solid cylinder whose height is 2.4 cm and diameter 1.4 cm, a conical cavity of the same height and same diameter is hollowed out. Find the total surface area of the remaining solid to the nearest cm2.
Height (h) of the conical part = Height (h) of the cylindrical part = 2.4 cm
Diameter of the cylindrical part = 1.4 cm
Therefore, radius (r) of the cylindrical part = 0.7 cm
Total surface area of the remaining solid will be
= CSA of cylindrical part + CSA of conical part + Area of cylindrical base
The total surface area of the remaining solid to the nearest cm2 is 18 cm2.
Why C.S.A. of cone is added instead of subtracting(cause we have to find T.S.A. of remaining part)???
The C.S.A of cone is added instead of subtracting as it is given in the question that the conical part is dig out of the cylindrical part because as we dig out the conical part it also forms a surface which is in the curved shape as you can see in the figure the inside of the object is also a surface.
Hope this helped...