A water storage tank has the shape of a cylinder with diameter 22 ft. It is mounted so that the circular cross-sections are vertical. If the depth of the water is 15 ft, what percentage of the total capacity is being used?
+36916 
From the diagram x = sqrt(11^2 -4^2) =10.24
So the area of the shaded triangles (there are two) = 2 x (1/2 x 4 x 10.24) = 40.96
Angle theta = arcsin 10.24/11 = 68.58
2 x theta =137.15 (central angle)
Total cross sectional area = pi r ^2 = pi 11^2 = 380.13
SECTOR area = 137.15/360 x 380.13 = 144.82 sqft
SECTOR - triangles = SEGMENT area = 144.82 - 40.96 = 103.86 sqft
How full is it ?
(Total area - SEGMENT area )/ Total area = (380.13-103.86)/380.13 = 72.67 % full
