Question

a metallic pipe is 0.7 CM thick inner radius of the pipe is 3.5 cm and the length is 5 dm find its total surface area​

Answer 1

Inner radius = 3.5 cm and outer radius = 4.2 cm

Length = 5 dm = 50 cm

Surface area of inside of pipe = (circumference)(length) = 2π(3.5 cm)(50 cm)

= 350π cm2

Surface area of outside of pipe = 2π(4.2 cm)(50 cm) = 420π cm2

Surface area of each end of pipe = outer area - inner area

= π(4.2 cm)2 - π(3.5 cm)2 = 5.39π cm2

Total surface area = 2(5.39π) cm2 + 350π cm2 + 420π cm2 = 775.39π cm2

Answer 2

Thickness of metallic pipe = 0.7 cm

Inner Radius (r) = 3.5 cm

External Radius (R) = 3.5 + 0.7 = 4.2 cm

Length of pipe (h) = 5 d m = 50 cm (1 d m = 10 cm)

Total surface area of pipe = 2π (r+ R ) ( h+ R - r)

or, Total surface area of pipe= 2x22/7(3.5+4.2)(50+4.2-3.5)

= 44/7 x 7.7 x 50.7

=2453.88cm^2

So the answer should be 2453.88cm^2