Q. 2
A rocket is in the form of a circular cylinder closed at the lower end with a cone of the same radius attached to the top. The cylinder is of radius 2.5 m and height 21 m and the cone has the slant height 8 m. Calculate the total surface area and the volume of the rocket.
Answer :
Radius of the cylinder portion (r) = 2.5 m
Height of the cylinder portion (h) = 21 m
∴ Surface area of the cylindrical portion = 2πrh
= 2 ×
× 2.5 × 21 m
= 330 m ………(1)
Radius of the conical portion (r) = 2.5 m
Slant height of the conical portion (l) = 8 m
∴ Curved surface area of the conical portion = πrl
= (22/7) × 2.5 × 8 m
= 62.86 m ……..(2)
Area of the circular top 
= (22/7) × 2.5 × 2.5 m2
= 19.64 m2 ……………(3)
∴
Total surface area of the rocket
= (330 + 62.86 + 19.64) m2 [From (1) , (2), (3)]
= 412.5 m2
Volume of the cylindrical portion 
h
= 412.5 m2
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