For a given ellipse, there are two foci, each of distance, c, from the centre of the ellipse and the two foci are along the line of the major axis.
The distance of the focus of an ellipse, from the center of the ellipse is given by
[tex]c= \sqrt{a^2-b^2} [/tex]
where: a is the length of the major axis and b is the length of the minor axis.
Thus, [tex]c= \sqrt{20^2-16^2} = \sqrt{400-256} = \sqrt{144} =12 \ feet[/tex]
Therefore, the distance apart of the two foci is given by
2c = 2(12) = 24 feet.
