Circumference, In Terms of Pi - Set 1

The circumference of a circle, "C" is the distance around a circle.  The diameter, "d" is the longest distance across a circle and passes through the center of the circle.  The radius, "r", is the distance from the circle to the center of the circle.  A diameter is made of 2 radii.  There are 2 formulas to find the circumference of a circle, Circumference = pi * diameter     and  Circumference = 2 * pi * r.  The symbol for pi is the Greek letter, , and is typically given the value of 3.14.  Leaving an answer as is called 'leaving  the circumference in terms of pi'.  For the problems in this problem set, you will be given the radius of a circle and you are to find the circumference, leaving the answer in 'in terms of pi'.