This is because the material the ballon is made of is shaped differently.
The ballon will stretch and try to achieve a perfect round shape, but can not due to limitations in the way the ballon is made.
One can however buy balloons that are almost perfectly round when inflated.
it is perfectly round.
The shape of the balloon is determined by the shape of the deflated rubber and the thickness of the rubber. The neck is usually thicker than the body, thus the body will expand far more than the neck. The pressure exerted upon the air by the balloon's elasticity creates the final inflated shape. If the thickness in the body of the balloon varies, the balloon will not be perfectly round. The thickness of the neck rubber forces the balloon to be more pear-shaped than spherical.
Yes
yes
Assuming the balloon is perfectly spherical and that the 12" you state refers to the diameter of the balloon then it is obviously 6". If you can't assume any of the above then your question cannot be answered.
yes
pooey in the looey
A sphere.
Is a circle.
A circle or a sphere
they'll both hold the same amount!
Full Moon