Question

A metal pipe is 77 cm long. In the horizontal cross section of this pipe, the internal and external diameters of the pipe are respectively 4 cm and 4.4 cm. Find
1. internal curved surface area
2. external curved surface area
3. total surface area

Answer 1

Hope this would help☺

Answer 2

$\huge\mathfrak{Solution:}$

We have,

Internal radius r of the pipe = 4/2 = 2 cm

External radius R of the pipe = 4.4/2 = 2 cm

Length of the pipe = 77 cm

(i) Area of internal curved surface of the pipe

= 2 × pi × r × h

= 2 × 22/7 × 2 × 77 cm^2

= 968 cm^2

(ii) Area of external curved surface of the pipe

= 2 × pi × R × h

= 2 × 22/7 × 4.4 × 77 cm^2

= 1064.8 cm^2

(iii) Area of rings on both ends of the pipe

= 2 × pi × (R^2 - r^2)

= 2 × 22/7 × (2.2 - 2) cm^2

= 44/7 × [(2.2 + 2) (2.2 - 2)] cm^2

= 44/7 × 4.2 × 0.2

= 44/7 × 84/100 cm^2

= 44 × 12 / 100 cm^2

= 5.28 cm^2

Hence, total surface area of the pipe

= (968 + 1064.8 + 5.28) cm^2

= 2038.08 cm^2

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HOPE IT HELPS ❤❤