Question 470340
Let 2a be length of major axis of ellipse.
Let 2b be length of minor axis of ellipse.
At either end of these axis, there are 2 tangent walkways each 3-feet wide
Six feet on each end which makes 12 feet. Subtract 12 from length and width of park to find dimensions of ellipse.
2a = 87 - 12 = 75 --> a = 37.5
2b = 42 - 12 = 30 --> b = 15
The foci are located length c from center, where {{{c^2 = a^2 - b^2}}}
{{{c^2 = 37.5^2 - 15^2 = 1181.25}}}
{{{c = 34.369}}}
The radius of small fountain is distance from focus point to edge of ellipse.
r = a - c 
r = 37.5 - 34.369 = 3.13
Radius of grand fountain is twice that of smaller fountain
R = 2*r = 2*3.13 = 6.26
Therefore, the desired radii are 3.13 ft. and 6.26 ft.