Question

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A metallic pipe is 0.7 cm thick. Inner radius of the pipe is 3.5 cm and length is
5 dm. Find its total surface area.
[Hint: Total surface area = Inner surface area + Outer surface area + Area of two rims​

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