Question

A metal pipe is 77 cm long. The inner diameter of a cross
section is 4 cm, the outer diameter being 4.4 cm
(see Fig. 13.11). Find its
(1) inner curved surface area,
(i) outer curved surface area,
(iii) total surface area.
​

Answer 1

ANSWER:

Given, A metal pipe is 77 cm. long

Inner Diameter = 4cm i.e. r = 2cm

Outer diameter = 4.4cm i.e. R = 2.2cm

(i) inner curved surface area = 2πrh

= 2 × 3.14 × 2 × 77

= 967.6cm2

(ii) outer curved surface area = 2πRh

= 2 × 3.14 × 2.2 × 77

= 1063.8cm2

(iii) total surface area = 2πrh + 2πrh + 2π(R2 – r2)

= 967.6 + 1063.8 + 2 × 3.14 × (2.22 – 22)

= 2036.6cm2