The areas of the surface of water for full basin and area for the surface when the depth is 10 inches are in the ratio 25^2 : 10^2 = 6.25 : 1. (because the depth of the water = radius of the water when the basin is full).
The area for a full basin = pi r^2 = 625pi in^2.
So the area when depth is 10 inches = 625pi / 6.25 = 100pi in^2.
The volume of a sphere, V = (4/3)(PI)(R^3)
Let k = (4/3)(PI)
Therefore, V = k (R^3)
Let R’ = new radius = 2R
V’ =k (R’^3)
= k (2R)^3
= 8 k R^3
= 8 V
The volume would be eight time the original volume.