cm is length, ml is cm3 which is 3 dimensional. you cannot compare length with volume
1 Inch equals 2.54cm, so 81cm would do 31.89 inches
2.657 feet.
it is 81cm
The circumference = 2 x r x pi If your diamter is 81cm then your circumference is 254.5cm If your radius is 81cm then your circumference is 508.9cm
Approximately 12.73cm
if you have a picture you could count around the square
Well let say the average person in 81cm wide (32 in), and 1.4km is 140 000cm140 000/81=1728 people
That is 3.75 ml.
1900 ml
That is 4,250 ml.
That is 600,000 ml.
That is 12,000 ml.