Question

find the whole surface area of a hollow cylinder open at both and whose external diameter is 14 cm , thickness is 2 cm and height 20 cm​

Answer 1

Answer:

Given internal diameter of hollow cylinder =14 cm.

∴ Internal radius (r2) = 7 cm

Width of the cylinder = 2 cm

∴ External radius (r1) = 7 + 2 = 9 cm

Height (h) 26 cm.

Total surface area of cylinder

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Answer 2

Answer:

The whole surface area of a hollow cylinder open at both and whose external diameter is 14 cm , thickness is 2 cm and height 20 cm​ is 80π.

Step-by-step explanation:

Given for the hollow cylinder with open at both ends, length is h = 20 cm, external diameter is 14 cm and the thickness is 2 cm.

The external radius is $r_1 =7$ cm

and the internal radius is $r_2 =7-2=5$ cm.

Now the total surface area of the hollow cylinder will be,

$=2 \times \pi \times (r_1 - r_2 )\times h\\=2\times \pi (7-5)\times20\\=2\times \pi \times2 \times20\\=2\times \pi \times40$

$=80 \pi sq.cm.$

So, the whole surface area of a hollow cylinder open at both side is 80π.