What is 2 times pi times r?

pi is 3.14 or 22/7.

What is r?

"2 times pi times r", which can be written as "2*pi*r", represents the circumference of a circle. This is the distance around the circle (aka perimeter)

r is the radius of the circle

if you know the diameter then you can divide the diameter in half to get the radius (example: diameter is 10 so the radius is 5)

R is the radius of the circle