In this page curved surface area solution4 we are going to see solution of some practice questions.
Question 8
The external surface area of a
hollow cylinder is 540 Π cm².Its internal diameter is 16 cm and height
is 15 cm. Find the total surface area.
Solution:
External surface area of cylinder = 540 Π cm²
2 Π R h = 540 Π cm²
Internal radius (r) = 16/2 = 8 cm
height (h) = 15 cm
2 x Π x R x h = 540 Π
2 x Π x R x 15 = 540 Π
= 540 Π x (1/2) x (1/Π) x (1/15)
= 270/(15)
R= 18
Total surface area = 2 Π (R + r) (R - r + h)
= 2 Π (18 + 8) (18 - 8 + 15)
= 2 Π (26) (25)
= 1300 Π cm²
Total surface area of the cylinder = 1300 Π cm²
Question 9
The external diameter of the cylindrical shaped iron pipe is 25 cm and its length is 20 cm. If the thickness of the pipe is 1 cm, find the total surface area of the pipe.
Solution:
External radius of the pipe (R) = 12.5 cm
height of the pipe (h) = 20 cm
thickness of the pipe (w) = 1 cm
To find total surface area of the cylinder we have to find the internal radius (r)
W = R - r
1 = 12.5 - r
r = 12.5 - 1
r = 11 .5 cm
Total surface area = 2 Π (R + r) (R - r + h)
= 2 Π (12.5 + 11.5) (12.5 - 11.5 + 20)
= 2 (22/7) (24) (21)
= 2 (22) (24) (3)
= 3168 cm²
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