In this problem they give rocket structure and rocket structure is the combination of cone and cylinder structure. This question form RS Aggarwal book page number 787 exercise17A chapter volume and surface area of solid.
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A rocket is in the form of a circular cylinder closed at the lower end and a cone of the same radius is attached to the top. The radius of the cylinder is 2.5 m, its height is 21 m and the slant height of the cone is 8 m. Calculate the total surface area of the rocket.
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Radius of the cylinder = 2.5 m
Height of the cylinder = 21 m
Curved surface area of the cylinder = 2πrh
= 2 * 22/7 * 2.5 * 21
= 330 m²
Radius of the cone = 2.5 m
Slant height of the cone = 8 m
Curved surface area of the cone = πrl
= 22/7 * 2.5 * 8
= 62. 86 m²
Area of circular base = πr²
= 22/7 * 2.5
= 19. 643 m²
∴ Total surface area of rocket = 330 +62. 86 +19. 643
∴ Total surface area of rocket= 412. 503 m²