& A metal pipe is 77 cm long, the inner diamcter of the cross-section

1.	& A metal pipe is 77 cm long, the inner diamcter of the cross-section is 4 cm and the outer diamcter is4.8 cm. Find the (i) inner curved surface arca (ii) outer curved surface area i) total surface area
Answer» Here, h = 77 cm, Outer radius (R) = 4. 4/ 2cm = 2.2 cm, Inner radius (r) = 4/ 2 cm = 2 cm (i) Inner curved surface area of the pipe = 2πrh = 2 × 22/ 7 × 2 × 77 cm2 = 2 × 22 × 22 cm2=968 cm2Ans. (ii) Outer curved surface area of the pipe = 2πRh = 2 × 22/ 7 × 2.2 × 77 cm2= 44 × 24.2 cm2 = 1064.80 cm2Ans. (iii) Total surface area of the pipe = inner curved surface area + outer curved surface area + areas of the two base rings. = 2πrh + 2πRh + 2π (R2– r2) = 968 cm2+ 1064.80 cm2+ 2 × 22/ 7 [(2.2)2– 22] cm2 = 2032.80 cm2+ 5.28 cm2=2038.08 cm2Ans

& A metal pipe is 77 cm long, the inner diamcter of the cross-section is 4 cm and the outer diamcter is4.8 cm. Find the (i) inner curved surface arca (ii) outer curved surface area i) total surface area

Answer»

Here, h = 77 cm,

Outer radius (R) = 4. 4/ 2cm = 2.2 cm,

Inner radius (r) = 4/ 2 cm = 2 cm

(i) Inner curved surface area of the pipe

= 2πrh

= 2 × 22/ 7 × 2 × 77 cm2

= 2 × 22 × 22 cm2=968 cm2Ans.

(ii) Outer curved surface area of the pipe = 2πRh

= 2 × 22/ 7 × 2.2 × 77 cm2= 44 × 24.2 cm2

= 1064.80 cm2Ans.

(iii) Total surface area of the pipe = inner curved surface area + outer

curved surface area + areas of the two base rings.

= 2πrh + 2πRh + 2π (R2– r2)

= 968 cm2+ 1064.80 cm2+ 2 × 22/ 7 [(2.2)2– 22] cm2

= 2032.80 cm2+ 5.28 cm2=2038.08 cm2Ans