A metallic pipe is 0.7cm thick. Inner radius of the pipe is 3.5cm and length is 5dm.Find it's total surface area.

Question

It's a mensuration word problem of class 8th. Here we have to find total surface area of the metallic pipe.

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