Diameter of circle: 13/pi = 4.138 ft to 3 decimal places
circumference = pi*diameter so diameter = circumference/pi = 19.1 metres.
If the diameter is known, don't bother measuring the circumference.Simply multiply the diameter by 'pi'.
Either pi times the diameter or pi times twice the radius (which is the diameter)
Just over 25' ( 8 x pi)
39 inches / pi = 12.4 inches
19 pi, ie 19 x 3.1415 = 59.69
30/pi = just over 9.5 cm
7/8 inch circle has a diameter of 7/8 and a radius of 7/16=.4375 circumferance of a circle = 2*pi*radius = 2*3.14*.4375 =2.7475 or 7*pi/8
The circumference of a circle divided by its own diameter will leave you with pi which is about 3.142 correct to three decimal places.
R(10) If you know the Circumferance, divide it by Pi (about 3.14). That will tell you the diameter. Half the diameter equals the radius.
Easy. The circumference of a circle is found by multiplying the diameter by Pi (3.1416). So, in this case: 9 x Pi (3.1416) =a circumference of 28.2744