Question

A rectangular strip of size 25 CM x 7 cm is rotated about the longer side find the volume and the whole surface of the solid does generated

Answer 1

If we roll a rectangle we will get a cylinder

The cylinder formed will have:-

Diameter as 7cm      and       height as 25cm

So radius is 7/2=3.5

Therefore volume=πr²h

                              =22/7 x 7/2  x  7/2 x 25

                              =962.5cm³

Whole surface area will be area of rectangle as the CSA of the cylinder is only formed

Therefore:-(by applying any formula area of rectangle or CSA of cylinder we get)

L x B = 25 x 7 = 175cm²

CSA of cylinder = 2πrh

                        =2 x 22/7 x 7/2 x 25

                        = 175cm²

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