Question

How yo find length of these Rounded Pipe
R=21 cm
L=???​

Answer 1

It's too simple!

Since outer radius is 21 cm

Total area occupied pi * r^2

A = pi * (21 cm) ^2 = 441 pi cm^2

Let's assume that

Since only outer radius is given we will assume inner radius to be 0

Now taking a variable radius r

21 cm >= r >= 0

So we will basically integrate!

Now variable of integration is r

Length of a round of radius r will be :-

2 * pi * r

So ,

dl = 2 * pi * r

Integrating