Question

a hollow metallic cylinder is open at both the ends and is of length 8cm if the thickness of the metal is 2cm and external diameter of the cylinder is 10cm find the whole csa of the cylinder(\pi =3.14) [hint:curved surface=internal curved surface+external curved surface]

Answer 1

We know, C.S.A. of hollow cylinder = (internal surface area + ext. surface area)
so, C.S.A. = (2pie×r×h + 2pie×R×h)
external radius = R
internal radius = r

A.T.Q.:-
h = 8cm
R = 10/2cm = 5cm
r = 5cm-2cm=3cm(thickness of cylinder is 2cm)

Now,
Internal surface area:-
= 2pie×r×h
= 2×3.14×3×8
= 6.28×24
= 140.72 cm square ------ ( i )

Now,
External surface area:-
= 2pie×r×h
= 2×3.14×5×8
= 6.28×40
= 251.2 cm square ------- ( ii )

ADDING EQUATION (I) AND (II) WE GET:-

= (251.2+140.72) cm square
= 391.82 cm square. -----------------ANS.

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