calculate the radius of a circle, with a center of 0.00cm, within which there is a 90% chance that your,,,

its asking the above question calculate the radius of a circle, with a center of 0.00cm, within which there is a 90% chance that your marble will hit the target from a height of two meters. I simply don’t know how to set this up. There is a second part that says calculate which ring on your target (1×1) a square should be placed for it to be hit.