I would use a measuring tape because it is easier to wrap it around a baby's head.
A cloth tape measure.
Because the circumference of a circle isn't a straight line its hard to measure, even if you have a flexi-ruler, your never going to be able to line it up to get an exact measurement. Therefore its much easier to measure the diameter and use the formula
depends how big it is
Of a circle? It's the perimeter of the circle. Imagine putting measuring tape around a circle, the you would get a circumference
If you measure the arc longer than it really is, the calculated circumference would be artificially increased. This is because the circumference is derived from the total length of all arcs measured; thus, inaccurately measuring an arc longer than its actual length would lead to an overall larger circumference value. The discrepancy would directly correlate to the extent of the error in the arc measurement. Consequently, the final circumference would not accurately reflect the true dimensions of the circle.
An AU is much larger than any distance on Earth. Earth's equatorial circumference is about 0.00027 . So measuring distances on Earth in AU would be like measuring the sizes of small animals in miles.
You would measure it in centimeters.
Measuring tape.
measuring tape
a tape measure
0.16 measuring spoons of turmeric has been present in 500mg of turmeric in standard measuring spoons.
They can measure the circumference of the pipe and divide it by pi or 3.14 to get an approximate answer