![geometry - Why the perimeter of a ring is $2\pi(R+r)$ and not $2\pi(R-r)$ ? where $R$ is the bigger circle radius and $r$ is smaller circle radius - Mathematics Stack Exchange geometry - Why the perimeter of a ring is $2\pi(R+r)$ and not $2\pi(R-r)$ ? where $R$ is the bigger circle radius and $r$ is smaller circle radius - Mathematics Stack Exchange](https://i.stack.imgur.com/Zd3AN.png)
geometry - Why the perimeter of a ring is $2\pi(R+r)$ and not $2\pi(R-r)$ ? where $R$ is the bigger circle radius and $r$ is smaller circle radius - Mathematics Stack Exchange
![Q: Is it a coincidence that a circles circumference is the derivative of its area, as well as the volume of a sphere being the antiderivative of its surface area? What is Q: Is it a coincidence that a circles circumference is the derivative of its area, as well as the volume of a sphere being the antiderivative of its surface area? What is](https://www.askamathematician.com/wp-content/uploads/2013/02/circumference.jpg)
Q: Is it a coincidence that a circles circumference is the derivative of its area, as well as the volume of a sphere being the antiderivative of its surface area? What is
![the inner and outer circumference of a circular ring is 44cm and 88cm find the width of the ring - Maths - Perimeter and Area - 12316061 | Meritnation.com the inner and outer circumference of a circular ring is 44cm and 88cm find the width of the ring - Maths - Perimeter and Area - 12316061 | Meritnation.com](https://s3mn.mnimgs.com/img/shared/ck-files/ck_5867d68e039a0.png)