Awater reservoir is in the form of a right circular cone. the cone is 21 ft deep and has a radius of 7ft. water has collected in the cone to a depth of x ft, and has a radius of 3ft. find the volume of the water

Check the picture below.

so notice,  in a cone the height and radius are always at a ratio of each other in a right-triangle, since the water level, in red, makes a similar triangle with the cone's volume, let's use proportions to get "x".

area = length x width

length = 2 x width

32 = 2 x width x width

32 = 2 x width^2

36 = width ^2  

width = 6

length = 12

area is 32

perimeter = 2 x 12 + 2 x 6 = 24 + 12 = 36

step-by-step explanation:

may i see the picture? it would a lot, xox